Fulltext

5 downloads 12092 Views 10MB Size Report
Sep 19, 2003 ... F. Manso, P. Rosnet, L. Royer, P. Saturnini, G. Savinel and F. Yermia. Columbus ...... Figure 2.1: A schematic diagram of the cross section of a unit cell. 'a' and 'b' ... trigger scintillators (SC1-SC2 and SC3-SC4) available at the T10 beam line which had an overlap area ..... convection cooling by chilled air.

CERN / LHCC 2003–038 Addendum 1 to ALICE TDR 6 19 September 2003

ALICE Addendum to the

Technical Design Report of the

Photon Multiplicity Detector (PMD)

Cover design by CERN Desktop Publishing Service Printed at CERN September 2003 ISBN 92-9083-215-0

i

ALICE Collaboration

Alessandria, Italy, Facolt`a di Scienze dell’Universit`a: P. Cortese, G. Dellacasa, L. Ramello and M. Sitta. Aligarh, India, Physics Department, Aligarh Muslim University: N. Ahmad, S. Ahmad, T. Ahmad, W. Bari, M. Irfan and M. Zafar. Athens, Greece, University of Athens, Physics Department: P. Crhistakoglou, A. Petridis, M. Spyropoulou-Stassinaki and M. Vassiliou. Bari, Italy, Dipartimento di Fisica dell’Universit`a and Sezione INFN: M. Caselle, G. De Cataldo, D. Di Bari, D. Elia, R.A. Fini, B. Ghidini, V. Lenti, V. Manzari, E. Nappi 1) , F. Navach, C. Pastore, F. Posa and I. Sgura. Bari, Italy, Politecnico and Sezione INFN: F. Corsi, D. De Venuto, R. Dinapoli, G. Lisco, C. Marzocca and E. Monno. Beijing, China, China Institute of Atomic Energy: X. Li, Z. Liu, S. Lu, Z. Lu, Q. Meng, B. Sa, J. Yuan, J. Zhou and S. Zhou. Bergen, Norway, Depatment of Physics, University of Bergen: A. Klovning, J. Nystrand, P. Pommeresche, D. R¨ohrich, K. Ullaland A.S. Vestboe Z. Yin. Bergen, Norway, Bergen University College, Faculty of Engineering: K. Fanebust, H. Helstrup and J.A. Lien. Bhubaneswar, India, Institute of Physics: R.K. Choudhury, A.K. Dubey, D.P. Mahapatra, D. Mishra, S.C. Phatak and R. Sahoo. Birmingham, United Kingdom, School of Physics and Space Research, University of Birmingham: D. Evans, G.T. Jones, P. Jovanovi´c, J.B. Kinson, R. Lietava, O. Villalobos Baillie and A. Jusko. Bologna, Italy, Dipartimento di Fisica dell’Universit`a and Sezione INFN: A. Alici, F. Anselmo, P. Antonioli, G. Bari, M. Basile, y.W. Baek, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, E. Cerron-Zeballos, L. Cifarelli, F. Cindolo, M. Corradi, D. Falchieri, A. Gabrielli, E. Gandolfi, P. Giusti, D. Hatzifotiadou, G. Laurenti, M.L. Luvisetto, A. Margotti, M. Masetti, S. Morozov, R. Nania, P. Otiougova, F. Palmonari, A. Pesci, F. Pierella, A. Polini, G. Sartorelli, G. Scioli, G.P. Vacca, G. Valenti, G. Venturi, M.C.S. Williams and A. Zichichi. Bratislava, Slovakia, Comenius University, Faculty of Mathematics, Physics and Informatics: ˇ y, P. Chochula, R. Janik, S. Kapusta, L. Lucan, M. Pikna, J. Piˇsu´ t, N. Piˇsu´ tov´a, B. Sitar, V. Cern´ P. Strmeˇn, I. Szarka and M. Zagiba. Bucharest, Romania, National Institute for Physics and Nuclear Engineering: C. Aiftimiei, A. Andronic, V. Catanescu, M. Ciobanu, M. Duma, C.I. Legrand, D. Moisa, M. Petrovici and G. Stoicea.

ii Budapest, Hungary, KFKI Research Institute for Particle and Nuclear Physics, Hungarian Academy of Sciences: E. Denes, B. Eged, Z. Fodor, T. Kiss, G. Palla, C. Soos, J. Sulyan, and J. Zimanyi. Cagliari, Italy, Dipartimento di Fisica dell’Universit`a and Sezione INFN: C. Cicalo, A. De Falco, M. Floris, M.P. Macciotta-Serpi, A. Masoni, G. Puddu, S. Serci, E. Siddi and G. Usai. Catania, Italy, Dipartimento di Fisica dell’Universit`a and Sezione INFN: A. Badal`a, R. Barbera, G. Lo Re, A. Palmeri, G.S. Pappalardo, A. Pulvirenti and F. Riggi. CERN, Switzerland, European Laboratory for Particle Physics: Y. Andres, G. Anelli, I. Augustin, A. Augustinus, J. Baechler, P. Barberis, J.A. Belikov 2) , L. Betev, A. Braem, R. Brun, M. Burns, P. Buncic, R. Campagnolo, M. Campbell, F. Carena, W. Carena, F. Carminati, N. Carrer, C. Cheshkov, P. Chochula, J. Chudoba, J. Cruz de Sousa Barbosa, (IST Lisboa) M. Davenport, G. de Cataldo, J. de Groot, A. Di Mauro, R. Dinapoli, R. Divi`a, C. Engster, S. Evrard, C. Fabjan, A. Fasso, D. Favretto, L. Feng,also Beijing F. Formenti, E. Futo 5) , A. Gallas Torreira, A. Gheata, I. Gonzalez-Caballero, (CSIC-UC, Santander) C. Gonzalez Gutierrez, C. Gregory, M. Hoch, H. Hoedelmoser, P. Hristov, M. Ivanov, L. Jirden, A. Junique, W. Klempt, A. Kluge, M. Kowalski 20) , T. Kuhr, L. Leistam, C. Lourenc¸o, J.-C. Marin, P. Martinengo, A. Masoni, T. Meyer, A. Mohanty, M. Morel, A. Morsch, B. Mota, H. Muller, L. Musa, P. Nilsson, D. Perini, A. Peters, D. Picard, F. Piuz, ˇ r´ık, P. Saiz, J.-C. Santiard, S. Popescu, F. Rademakers, J.-P. Revol, P. Riedler, E. Rosso, K. Safaˇ 19) K. Schossmaier, J. Schukraft, Y. Schutz , E. Schyns, P. Skowronski, C. Soos, G. Stefanini, R. Stock18) , D. Swoboda, P. Szymanski, H. Taureg, M. Tavlet, P. Tissot-Daguette, P. Vande Vyvre, C. Van Der Vlugt, J.-P. Vanuxem and A. Vascotto. Chandigarh, India, Physics Department, Panjab University: M.M. Aggarwal, A.K. Bhati, A. Kumar, M. Sharma and G. Sood Clermont-Ferrand, France, Laboratoire de Physique Corpusculaire (LPC), IN2P3-CNRS and Universit´e Blaise Pascal: IN2P3: A. Baldit, V. Barret, N. Bastid, G. Blanchard, J. Castor, P. Crochet, F. Daudon, A. Devaux, P. Dupieux, P. Force, B. Forestier, A. Genoux-Lubain, C. Insa, F. Jouve, L. Lamoine, J. Lecoq, F. Manso, P. Rosnet, L. Royer, P. Saturnini, G. Savinel and F. Yermia. Columbus, U.S.A., Department of Physics, Ohio State University: T.J. Humanic, I.V. Kotov, M. Lisa, B.S. Nilsen and E. Sugarbaker. Columbus, U.S.A., Ohio Supercomputer Centre: D. Johnson Copenhagen, Denmark, Niels Bohr Institute: I. Bearden, H. Bøggild, P. Christiansen, J.J. Gaardhøje, O. Hansen, A. Holm, B.S. Nielsen and D. Ouerdane. Cracow, Poland, Henryk Niewodniczanski Institute of Nuclear Physics, High Energy Physics Department: J. Bartke, E. Gładysz-Dziadu´s, E. Kornas M. Kowalski, A. Rybicki and A. Wroblewski 16)

iii Darmstadt, Germany, Gesellschaft f¨ur Schwerionenforschung (GSI): A. Andronic, D. Antonczyk, H. Appelsh¨auser, E. Badura, E. Berdermann, P. Braun-Munzinger, O. Busch, M. Ciobanu, H.W. Daues, P. Foka, U. Frankenfeld, C. Garabatos, H. Gutbrod, C. Lippman, P. Malzacher, A. Marin, D. Mi´skowiec, S. Radomski, H. Sako, A. Sandoval, H.R. Schmidt, K. Schwarz, S. Sedykh, R.S. Simon, H. Stelzer, G. Tziledakis and D. Vranic. Darmstadt, Germany, Institut f¨ur Kernphysik, Technische Universit¨at ∗) : A. F¨orster, H. Oeschler and F. Uhlig. Frankfurt, Germany, Institut f¨ur Kernphysik, Johann Wolfgang Goethe-Universit¨at: C. Adler, J. Berger, A. Billmeier, P. Buncic, T. Dietel, D. Flierl, M. Ga´zdzicki, Th. Kolleger, S. Lange, R. Renfordt, R. Stock1) , H. Str¨obele and C. Str¨uck. Gatchina, Russia, St. Petersburg Nuclear Physics Institute: Ya. Berdnikov, A. Khanzadeev, N. Miftakhov, V. Nikouline, V. Poliakov, E. Rostchine, V. Samsonov, O. Tarasenkova, V. Tarakanov, M. Zhalov. Heidelberg, Germany, Kirchhoff Institute for Physics: V. Angelov, M. Gutfleisen, V. Lindenstruth, R. Panse, R. Reichling, R. Schneider, T. Steinbeck H. Tilsner and A. Wiebalck. Heidelberg, Germany, Physikalisches Institut, Ruprecht-Karls Universit¨at: C. Adler D. Emschermann, P. Gl¨assel, N. Herrmann, Th. Lehmann, W. Ludolphs, T. Mahmoud, J. Milosevic, K. Oyama, V. Petr´acˇ ek, M. Petrovici, I. Rusanov, R. Schicker, J. Slivova, H.C. Soltveit, J. Stachel, B. Vulpescu, B. Windelband and S. Yurevich. Jaipur, India, Physics Department, University of Rajasthan: S. Bhardwaj, R. Raniwala and S. Raniwala. Jammu, India, Physics Department, Jammu University: S.K. Badyal, A. Bhasin, A. Gupta, V.K. Gupta, S. Mahajan, L.K. Mangotra, B.V.K.S. Potukuchi and S.S. Sambyal. JINR, Russia, Joint Institute for Nuclear Research: P.G. Akichine, V.A. Arefiev, B.V. Batiounia, Y.A. Belikov, G.S. Chabratova, S.A. Chernenko, V.K. Dodokhov, L.G. Efimov, V.G. Kadychevsky, E.K. Koshurnikov, V.L. Lioubochits, V.I. Lobanov, L.V. Malinina, P.V. Nomokonov, Y.A. Panebrattsev, V.N. Penev, I. Roufanov, A.I. Shklovskaya, M.K. Suleimanov, A.S. Vodopianov, V.I. Yurevich, Y.V. Zanevsky, S.A. Zaporojets and A.I. Zinchenko. V. Kuznetsov9) and V. Shestakov9) . Ts. Baatar10) , and R. Togoo10) . T. Grigalashvili11) , M. Nioradze12) , and Y. Tevzadze12) . M. Haiduc13) and D. Hasegan13) , Jyv¨askyl¨a, Finland, Department of Physics, University of Jyv¨askyl¨a and Helsinki Institute of Physics: ¨ J. Aysto, M. Bondila, V. Lyapin, M. Oinonen, V. Ruuskanen, H. Sepp¨anen and W. Trzaska.

iv Kharkov, Ukraine, National Scientific Centre ‘Kharkov Institute of Physics and Technology’: G.L. Bochek, A.N. Dovbnya, V.I. Kulibaba, N.I. Maslov, S.V. Naumov, V.D. Ovchinnik, S.M. Potin and A.F. Starodubtsev. Kharkov, Ukraine, Scientific and Technological Research Institute of Instrument Engineering: V.N. Borshchov, O. Chykalov, L. Kaurova, S.K. Kiprich, L. Klymova, O.M. Listratenko, N. Mykhaylova, M. Protsenko, o. Reznik and V.E. Starkov. Kiev, Ukraine, Department of High Energy Density Physics, Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine: Olexander BORYSOV I. Kadenko, Y. Martynov, S. Molodtsov, O. Sokolov, Y. Sinyukov and G. Zinovjev. Kolkata, India, Saha Institute of Nuclear Physics: P. Bhattacharya, S. Bose, S. Chattopadhyay, N. Majumdar, S. Mukhopadhyay, A. Sanyal, S. Sarkar, P. Sen, S.K. Sen, B.C. Sinha and T. Sinha. Kolkata, India, Variable Energy Cyclotron Centre: Z. Ahammed, P. Bhaskar, S. Chattopadhyay, D. Das, S. Das, M.R. Dutta Majumdar, M.S. Ganti, P. Ghosh, B. Mohanty, B.K. Nandi, T.K. Nayak, P.K. Netrakanti, S. Pal, R.N. Singaraju, B. Sinha, M.D. Trivedi and Y.P. Viyogi. Koˇsice, Slovakia, Institute of Experimental Physics, Slovak Academy of Sciences and Faculty of ˇ arik University: Science, P.J. Saf´ J. B´an, M. Bombara, S. Fedor, M. Hnatiˇc, A. Jusko, I. Kr´alik, A. Kravˇca´ kov´a, F. Kriv´anˇ , M. Krivda, ˇ andor, J. Urb´an, S. Vok´al and J. Vrl´akov´a. G. Martinsk´a, B. Pastirˇca´ k1) , L. S´ Legnaro, Italy, Laboratori Nazionali di Legnaro: M. Cinausero, E. Fioretto, G. Prete, R.A. Ricci and L. Vannucci. Lisbon, Portugal, Departamento de F´ısica, Instituto Superior T´ecnico: P. Branco, R. Carvalho, J. Seixas and R. Vilela Mendes. Lund, Sweden, Division of Cosmic and Subatomic Physics, University of Lund: H.-A. Gustafsson, A. Oskarsson, L. Osterman, I. Otterlund and E.A. Stenlund. Lyon, France, Institut de Physique Nucl´eaire de Lyon (IPNL), IN2P3-CNRS and Universit´e Claude Bernard Lyon-I: B. Cheynis, L. Ducroux, J.Y. Grossiord, A. Guichard, P. Pillot, B. Rapp and R. Tieulent. Mexico, D.F. and Merida, Centro de Investigacion y de Estudios Avanzados del IPN; Universidad Nacional Autonoma de Mexico, Instituto de Ciencias Nucleares, Instituto de Fisica: J.R. Alfaro Molina, A. Ayala, A. Becerril, E. Belmont Moreno, G. Contreras Nuno, E. Cuautle, J.C. D’Olivo, G. Herrera Corral, I. Leon Monzon, J. Martinez Castro, A. Martinez Davalos, A. Menchaca-Rocha, L.M. Montano Zetina, L. Nellen, G. Paic 17) , J. Solano and A. Zepeda-Dominguez. Mexico, Morelia, Michoacan, Universidad Michoacana de Sn. Nicolas de Hidalgo: U. Cotti, L. Villasenor-Cendejas Mexico, Puebla, Benemerita Universidad Autonoma de Puebla: A. Fernandez Tellez, E. Gamez Flores, R. Lopez, S. Roman, M.A. Vargas, S. Vergara.

v Moscow, Russia, Institute for Nuclear Research, Academy of Science: M.B. Goloubeva, F.F. Gouber, O.V. Karavichev T.L. Karavicheva, A.B. Kourepin, A.I. Maevskaia, V.V. Marin, I.A. Pshenichnov, V.I. Razine, A.I. Rechetin, K.A. Shileev and N.S. Topilskaia. Moscow, Russia, Institute for Theoretical and Experimental Physics: A.N. Akindinov, V. Golovine, A.B. Kaidalov, M.M. Kats, I.T. Kiselev, S.M. Kisselev, E. Lioublev, M. Martemianov, A.N. Martemiyanov, P.A. Polozov, V.S. Serov, A.V. Smirnitski, M.M. Tchoumakov, I.A. Vetlitski, K.G. Volochine, L.S. Vorobiev and B.V. Zagreev. Moscow, Russia, Russian Research Center ‘Kurchatov Institute’: D. Aleksandrov, V. Antonenko, S. Beliaev, S. Fokine, M. Ippolitov, K. Karadjev, V. Lebedev, V.I. Manko, T. Moukhanova, A. Nianine, S. Nikolaev, S. Nikouline, O. Patarakine, D. Peressounko, I. Sibiriak, A. Tsvetkov, A. Vasiliev, A. Vinogradov, M. Volkov and I. Yushmanov. Moscow, Russia, Moscow Engineering Physics Institute: V.A. Grigoriev, V.A. Kapline and V.A. Loguinov. ¨ Munster, Germany, Institut f¨ur Kernphysik, Westf¨alische Wilhelms Universit¨at: C. Baumann, D. Bucher, R. Glasow, H. Gottschlag, N. Heine, K. Reygers, R. Santo, W. Verhoeven, J. Wessels and O. Zaudtke. !corrected on 8-8-03 Nantes, France, Laboratoire de Physique Subatomique et des Technologies Associ´ees (SUBATECH), Ecole des Mines de Nantes, IN2P3-CNRS and Universit´e de Nantes: L. Aphecetche, A. Boucham, K. Boudjemline, J.P. Cussonneau, H. Delagrange, M. Dialinas, C. Finck, B. Erazmus, M. Germain, P. Lautridou, F. Lef`evre, L. Luquin, L. Martin, G. Martinez, O. Ravel, C.S. Roy, Y. Schutz1) and A. Tournaire. The Netherlands, Subatomic Physics Department, Utrecht University and National Institute for Nuclear and High Energy Physics (NIKHEF): M. Botje, J.J.F. Buskop, A.P. De Haas, R. Kamermans, P.G. Kuijer, G. Nooren, C.J. Oskamp, Th. Peitzmann, E. Simili, R. Snellings, A.N. Sokolov and A. Van Den Brink Novosibirsk, Russia, Budker Institute for Nuclear Physics: A.R. Frolov and I.N. Pestov. Oak Ridge, U.S.A., Instrumentation and Controls Division, Oak Ridge National Laboratory: T. Awes, C.L. Britton, W.L. Bryan, J.W. Walker and A.L. Wintenberg. Orsay, France, Institut de Physique Nucl´eaire (IPNO), IN2P3-CNRS and Universit´e de Paris-Sud: L. Bimbot, P.F. Courtat, R. Douet, P. Edelbruck, D. Jouan, Y. Le Bornec, M. Mac Cormick, J. Peyr´e, J. Pouthas and N. Willis. Oslo, Norway, Department of Physics, University of Oslo: L. Bravina, G. Løvhøiden, B. Skaali, T.S. Tveter, J.c. Wikne and D. Wormald. Padua, Italy, Dipartimento di Fisica dell’Universit`a and Sezione INFN: F. Antinori, A. Dainese, D. Fabris, M. Lunardon, M. Morando, S. Moretto, A. Pepato, E. Quercigh, F. Scarlassara, G. Segato, F. Soramel 21) , R. Turrisi and G. Viesti. Prague, Czech Republic, Institute of Physics, Academy of Science: A. Beitlerova, J. Mareˇs, E. Mihokov´a, M. Nikl, K. P´ısˇka, K. Pol´ak and P. Z´avada.

vi Protvino, Russia, Institute for High Energy Physics: M.Yu. Bogolyubsky, G.I. Britvitch, G.V. Khaoustov, I.V. Kharlov, S.A. Konstantinov, N.G. Minaev, V.S. Petrov, B.V. Polichtchouk, S.A. Sadovski, P.A. Semenov, A.S. Soloviev and V.A. Victorov. ˇ z u Prahy, Czech Republic, Academy of Sciences of Czech Republic, Nuclear Physics Institute: Reˇ ˇ D. Adamov´a, S. Kouchpil, V. Kouchpil, A. Kugler, M. Sumbera, P. Tlust´y and V. Wagner. Rome, Italy, Dipartimento di Fisica dell’Universit`a ‘La Sapienza’ and Sezione INFN: S. Di Liberto, M.A. Mazzoni, F. Meddi, D. Prosperi and G. Rosa. Rondebosch, South Africa, University of Cape Town: J. Cleymans, R. Fearick and Z. Vilakazi. Saclay, France, Centre d’Etudes Nucl´eaires, DAPNIA: M. Anfreville, A. Baldisseri, H. Borel, D. Cacaut, E. Dumonteil, R. Durand, P. De Girolamo, J. Gosset, P. Hardy, V. Hennion, S. Herlant, F. Orsini, Y. P´enichot, H. Pereira, S. Salasca, F.M. Staley and M. Usseglio. Salerno, Italy, Dipartimento di Fisica ‘E.R.Caianiello’ dell’Universit´a and INFN: A. De Caro, S. De Pasquale, A. Di Bartolomeo, M. Fusco Girard, G. Grella, M. Guida, J. Quartieri, G. Romano, S. Sellitto D. Vicinanza and T. Virgili. Sarov, Russia, Russian Federal Nuclear Center (VNIIEF): V. Basmanov, D. Budnikov, V. Demanov, V. Ianowski, R. Ilkaev, L. Ilkaeva, A. Ivanov, A. Khlebnikov, A. Kouryakin, S. Nazarenko, V. Pavlov, S. Philchagin, V. Punin, S. Poutevskoi, I. Selin, I. Vinogradov, S. Zhelezov and A. Zhitnik. St. Petersburg, Russia, Institute for Physics of St. Petersburg State University, : M.A. Braun, G.A. Feofilov, S.N. Igolkine, A.A. Kolojvari, V.P. Kondratiev, P.A. Otyugova, O.I. Stolyarov, T.A. Toulina, F.A. Tsimbal, F.F. Valiev, V.V. Vetchernine and L.I. Vinogradov. Strasbourg, France, Institut de Recherches Subatomiques (IReS), IN2P3-CNRS and Universit´e Louis Pasteur: J. Baudot, D. Bonnet, J.P. Coffin, C. Kuhn, J. Lutz and R. Vernet. Trieste, Italy, Dipartimento di Fisica dell’Universit`a and Sezione INFN: V. Bonvicini, L. Bosisio, M. Bregant, P. Camerini, E. Fragiacomo, N. Grion, R. Grosso, G. Margagliotti, A. Penzo, S. Piano, I. Rachevskaya, A. Rachevski, R. Rui and A. Vacchi. Turin, Italy, Dipartimenti di Fisica dell’Universit`a and INFN: B. Alessandro, R. Arnaldi, S. Beol´e, P.G. Cerello, E. Chiavassa, E. Crescio, N. De Marco, A. Ferretti, M. Gallio, P. Giubellino, M. Idzik, A. Marzari-Chiesa, M. Masera, M. Monteno, A. Musso, D. Nouais, C. Oppedisano, A. Piccotti, F. Prino, L. Riccati, E. Scomparin, F. Tosello, E. Vercellin, A. Werbrouck and R. Wheadon. Warsaw, Poland, Soltan Institute for Nuclear Studies: A. Deloff, T. Dobrowolski, K. Karpio, M. Kozlowski, H. Malinowski, K. Redlich, T. Siemiarczuk, G. Stefanek8) , L. Tykarski and G. Wilk. Warsaw, Poland, University of Technology, Institute of Physics: Z. Chajecki, M. Janik, A. Kisiel, T.J. Pawlak, W.S. Peryt, J. Pluta, T. Traczyk, Z. Skowronski and P.Szarwas.

vii Worms, Germany, University of Applied Sciences Worms, ZTT: E.S. Conner and R. Keidel Wuhan, China, Institute of Particle Physics, Huazhong Normal University: X. Cai, F. Liu, F.M. Liu, H. Liu, Y. Liu, W.Y. Qian, X.R. Wang, T. Wu, C.B. Yang, H.Y. Yang Z.B. Yin, D.C. Zhou and D.M. Zhou. Yerevan, Armenia, Yerevan Physics Institute: M. Atayan, A. Grigorian, S. Grigoryan, H. Gulkanyan, A. Hayrapetyan, A. Harutyunyan, V. Kakoyan, Yu. Margaryan, M. Poghosyan, R. Shahoyan and H. Vardanyan. Zagreb, Croatia, Ruder Boˇskovi´c Institute: T. Anticic, K. Kadija and T.Susa. Zagreb, Croatia, University of Zagreb, Prirodoslovno-Matematicki Fakultet: R. Manger, M. Marusic, G. Nogo, R. Piskac and K. Puljic.

∗)

Applying to join ALICE. Also at CERN, Geneva, Switzerland. 2) On leave from JINR, Dubna, Russia. 3) On leave from IHEP, Protvino, Russia. 4) On leave from Comenius University, Bratislava, Slovakia. 5) On leave from Budapest University, Hungary. 6) On leave from Dipartimento di Fisica dell’Universit´ a and Sezione INFN, Padua, Italy. 7) Institut Universitaire de Technologie de Monluc ¸ on, Allier, France. 8) Institute of Physics, Pedagogical University, Kielce, Poland. 9) Research Centre for Applied Nuclear Physics (RCANP), Dubna, Russia. 10) Institute of Physics and Technology, Mongolian Academy of Sciences, Ulaanbaatar, Mongolia. 11) Institute of Physics, Georgian Academy of Sciences, Tbilisi, Georgia. 12) High Energy Physics Institute, Tbilisi State University, Tbilisi, Georgia. 13) Institute of Space Sciences, Bucharest, Romania. 14) Foundation of Fundamental Research of Matter in The Netherlands. 15) Utrecht University, Utrecht, The Netherlands. 16) Cracow Technical University, Poland. 17) Columbus, Department of Physics, Ohio State University, U.S.A. . 18) Frankfurt, Institut f¨ ur Kernphysik, Johann Wolfgang Goethe-Universit¨at Germany. 19) Laboratoire de Physique Subatomique et des Technologies Associ´ ees (SUBATECH), Ecole des Mines de Nantes, IN2P3-CNRS and Universit´e de Nantes. 20) Cracow, Henryk Niewodniczanski Institute of Nuclear Physics, High Energy Physics Department, Poland. 21) Udine, Univerist´ a degli Studi, Italy. 1)

Acknowledgements It is a pleasure to acknowledge the help of P. Ijzermans, S. Maridor and R. Veenhof during the intensive R&D and in the preparation of this Addendum to the TDR. The Collaboration wishes to thank all the technical and administrative staff involved during the preparation of the present Addendum to the TDR. We also thank the staff from the Desktop Publishing Service for their professional help. This work is being supported by the Department of Atomic Energy and the Department of Science and Technology of the Government of India.

ix

Contents 1

2

3

4

Introduction 1.1 Need for relocation . . 1.2 New location . . . . . . 1.3 Effect of Relocation . . 1.3.1 Particle density . . . 1.3.2 Granularity . . . . . 1.3.3 Particle flux . . . . 1.4 Basic design parameters 1.5 Progress since TDR . .

. . . . . . . .

. . . . . . . .

. . . . . . . .

. . . . . . . .

. . . . . . . .

. . . . . . . .

. . . . . . . .

. . . . . . . .

. . . . . . . .

. . . . . . . .

. . . . . . . .

. . . . . . . .

. . . . . . . .

. . . . . . . .

Modifications in detector design 2.1 Prototype fabrication and tests . . . . . . . . . . . 2.2 Results for charged particle detection . . . . . . . 2.2.1 Pulse height spectra and operating parameters 2.2.2 Variation of efficiency within a cell . . . . . . 2.2.3 Relative gains of cells . . . . . . . . . . . . . 2.3 Preshower characteristics . . . . . . . . . . . . . 2.4 Behaviour at high particle flux . . . . . . . . . . . 2.4.1 Prototype-3 using SPS beam . . . . . . . . . . 2.4.2 Prototype-2 using radioactive source . . . . . Detector description 3.1 Mechanical design . . . . . . . . . . . . 3.1.1 Unit modules and supermodules . . . 3.1.2 Cooling . . . . . . . . . . . . . . . . 3.1.3 Suspension mechanism and servicing 3.1.4 Connection to front-end electronics . 3.2 Electronics and readout . . . . . . . . . 3.2.1 MANAS chip . . . . . . . . . . . . 3.2.2 FEE Board . . . . . . . . . . . . . . 3.2.3 Readout chain : Patch bus . . . . . . 3.2.4 CROCUS . . . . . . . . . . . . . . . 3.2.5 Dead time . . . . . . . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

. . . . . . . . .

. . . . . . . .

1 1 2 2 2 3 3 5 5

. . . . . . . . .

7 7 8 8 10 10 11 12 12 13

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

15 15 15 18 20 21 21 21 23 23 24 24

Physics performance 4.1 Measurement of photon multiplicity . . . . . . . . . . . . . . . . . 4.1.1 Simulation framework . . . . . . . . . . . . . . . . . . . . . . 4.1.2 Reconstruction . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.3 Effect of upstream material : Deflection of original photon track 4.1.4 Occupancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.5 Results on photon reconstruction efficiency and purity . . . . . 4.2 Effect of relocation on the physics capability of PMD . . . . . . . 4.2.1 General comments on the effect of relocation . . . . . . . . . . 4.2.2 Transverse electromagnetic energy . . . . . . . . . . . . . . . 4.2.3 Azimuthal anisotropy and flow . . . . . . . . . . . . . . . . . 4.2.4 Event-by-event fluctuation . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

25 25 25 27 28 28 30 32 32 33 33 34

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

4.2.5 4.2.6 5

Study of disoriented chiral condensates using DWT analysis . . . . . . . . . . . . . . Window analysis for DCC searches . . . . . . . . . . . . . . . . . . . . . . . . . . .

36 40

Integration, time schedules and costs 5.1 Integration and servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Cost and time frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

41 41 42

References

43

1

1 Introduction The present document describes changes to the design of the Photon Multiplicity Detector (PMD) due to its changed position in the ALICE experiment after the submission of the Technical Design Report (TDR) [1] in Sept. 1999. The relocation of the PMD, described below, has resulted in modifications in the basic cell design and also changed the pseudorapidity coverage of the detector. In the present document we show, with the help of simulations and prototype test results, that the PMD in the new position will be able to function and accomplish its physics objectives as proposed in the TDR. Mechanical design, frontend electronics, readout and integration issues are also described for the modified detector configuration.

1.1 Need for relocation UPSTREAM

MATERIAL

PMD

The PMD described in the Technical Design Report [1] had been designed for use in the pseudorapidity region 1.8≤ η ≤2.6 and at a distance of 580 cm from vertex on the opposite side of Dimuon Spectrometer1 . The estimation of upstream material was based on the GEANT implementation of geometries of all detectors in the AliRoot simulation package as available at that time (1999). It had been observed that the beam pipe, which had a short Beryllium section and a large stainless steel (SS) section, was a major source of background for the PMD. Since the writing of the PMD TDR, integration of the inner detectors, in particular amount and routing of services, has been substantially refined. It has been subsequently realized that structural components and services of TPC and ITS introduce a large amount of material in front of the PMD. The thickness of upstream material in the (η, φ) plane, as implemented in AliRoot in Jan. 2001, is shown in Fig. 1.1. In the region η ≤2.3 the upstream material exceeded even 10 X 0 which essentially blocked a major part of the PMD acceptance. It was clear that a photon detector like the PMD could not be effectively used at the position proposed in the TDR. Hence it had to be moved to another position within ALICE.

ITS + TPC + Al−Pipe + Start

ITS services configuration : Symmetric on both sides

Figure 1.1: Thickness in units of X0 of the upstream material in front of PMD as in AliRoot in Jan. 2001. The negative value of η denotes detectors on the side opposite the Dimuon Spectrometer in ALICE. to new convention within ALICE the z and η values for detectors on the side opposite the Dimuon Spectrometer are taken as negative. We shall however use positive values in the present Addendum as in the TDR to avoid confusion. 1 According

Room for PMD in the eta region beyond 2.3

2

1

Introduction

1.2 New location It has been discussed and decided within the ALICE collaboration that the PMD should be relocated to a higher pseudorapidity region (η ≥ 2.3). From preliminary simulation results, it was also found useful to bring the detector closer to vertex, in front of the ion pump, which was supposed to be situated at 385 cm from the interaction point. The usefulness of the new location has been further enhanced by the decision of the Collaboration to use a Beryllium beam pipe up to the PMD position. Several deliberations within the ALICE Collaboration held during the period 2001-02 have led to establishing a “forward detector zone” around (340-380) cm from the interaction point, on the opposite side of the Dimuon Spectrometer. This zone, shown schematically in Fig. 1.2, has four detectors placed close to each other. The PMD is situated at 361.5 cm within this zone and has an envelope thickness of 14 cm, covering the psudorapidity region 2.3≤ η ≤3.5. The V0 detector, situated just in front of the PMD, covers a circular zone of 1 m diameter around the beam pipe. The Si3 plane of the FMD is situated in front of V0 detector. The T0 detector is situated behind the PMD within the hole region. Behind the PMD there is a gate valve and a structure which supports the T0,V0 and Si3 part of the FMD. The ion pump has since been removed.

I.P.

PMD

Figure 1.2: New location of the PMD within the ALICE magnet in the forward zone showing T0, V0 and Si3 part of the FMD.

1.3 Effect of Relocation 1.3.1 Particle density The most important effect of going closer to interaction point is an increase in particle density on the detector plane. Fig 1.3 shows the photon density at the new position of the PMD within the region 2.3 ≤ η ≤ 3.5, assuming a charged particle pseudorapidity density in central lead-lead collisions at the LHC energy of 8000. The PMD in the new location will be required to handle a particle density per unit area which is on average a factor of 5 higher compared to the TDR case. This necessitates finer granularity in the new position.

1.3

Effect of Relocation

10

3

2

Number/cm 2

10

1

10

-1

0

10

20

30

40 50 60 70 80 Radial distance (cm)

90 100

Figure 1.3: Photon density distribution at the new location (z=361.5 cm) of the PMD. Vertical bars denote the radii corresponding to η=2.3 (right) and η=3.5 (left).

1.3.2 Granularity In the proposed location the total area of the detector becomes much smaller because of moving closer to the interaction point. Due to increased particle density a modification in the granularity of the detector is required. It has been discussed in detail in the TDR that the honeycomb proportional counter design with extended cathode is best suited for preshower applications. We have gained considerable experience with this design particularly during the fabrication of a similar PMD for the STAR experiment at RHIC [2]. We have therefore retained the basic design of the cell and modified the geometry to handle the particle density at the new location. After preliminary simulation studies, the cell cross-section was fixed to about 1/5 of the original (TDR) value, the new value being 0.22 cm 2 . The cell depth has been reduced from 8 mm to 5 mm as a compromise between the need to restrict the transverse spread of preshower and to have reasonable signal for minimum ionizing particles in the proportional mode of operation.

1.3.3 Particle flux The PMD will face an increased particle flux in the new location. The count rate capability of the TDR prototype had been tested up to a primary particle flux of 1000/cm 2 /sec, which was considered adequate for that position. Table 1.1 shows the primary particle flux for the PMD in the old and new positions, based on luminosity figures adapted from Ref. [3] for various operating conditions in ALICE. The number of primary particles within the PMD acceptance was calculated based on the following informations: (a) the PMD intercepts about 5.7% of the particles of the whole event in the TDR acceptance and 6.3% of the particles in the new acceptance, and (b) the number of charged particles and photons are similar. The detector area in the two cases are 10 m 2 and 2 m2 respectively. The modified detector design will be required to handle larger count rates. This is described in Chapter 2.

4

1

Introduction

Table 1.1: Primary particle flux within the PMD acceptance for various running scenarios (cm−2 s−1 )

σt [mb] Rate [s−1 ] Nch /event TDR Case Particles on PMD Flux [cm−2 sec−1 ] New Location Particles on PMD Flux [cm−2 sec−1 ]

pp 3×1030 70 2×105 100

Ar-Ar 3×1027 3000 9×103 2400

Ar-Ar 1029 3000 3×105 2400

Pb-Pb 1027 8000 8×103 14200

12 24

274 25

274 822

1620 130

13 130

302 136

302 4530

1790 716

A1

A4

A2

A5

A3

A6

B1

B3

B5

B2

B4

B6

Figure 1.4: Layout of the PMD showing four supermodules of one of the planes. Each supermodule has six unit modules. The outer circle represents full azimuthal coverage in the region 2.3 ≤ η ≤3.5.

1.4

Basic design parameters

5

1.4 Basic design parameters The PMD, as described in the TDR, has two planes of detectors with lead converter placed in between them. The front plane (closer to the interaction point)acts as a charged particle veto and the plane behind the converter is the preshower detector. The mechanical configuration of the detector supermodules has been modified to a rectangular shape which is relatively easier to handle compared to the rhombus shape described in TDR. This is discussed in Chapter 3. The concept of unit modules (UM) and supermodules (SM) have been retained. But due to smaller size, the number of cells within a unit module are much larger and the total number of supermodules are smaller. High voltage segmentation is provided at the unit module level. The detector has two planes for charged particle veto and preshower detection and splits vertically into two parts. The layout of PMD is shown in Fig. 1.4. Table 1.2 provides a comparison of basic design parameters of the PMD in the new location with that given in the TDR. The detector has full azimuthal coverage for the region 2.3 ≤ η ≤ 3.5. Regions of the detector outside the coverage will not be instrumented. Table 1.2: Comparison of basic parameters of the TDR and modified designs Parameter Technology Number of planes Distance from vertex η-coverage Active area Cell cross-section Cell depth (gas depth) No. of readout channels No. of supermodules per plane No. of unit modules in a SM No. of cells in a UM No. of HV channels Thickness of Pb-converter Thickness of SS support plate Total weight

TDR Extended cathode honeycomb veto+preshower 580 cm 1.8–2.6 10 m2 1 cm2 8 mm 200,000 26 9 576 52 1.5 cm 0.5 cm 6000 kg

Present Extended cathode honeycomb veto+preshower 361.5 cm 2.3–3.5 2 m2 0.22 cm2 5 mm 182,000 4 6 4608 48 1.5 cm 0.5 cm 1200 kg

1.5 Progress since TDR In addition to prototype tests and simulation studies for the modified detector, the following work has been carried out to gain experience with the detector and to study its performance in ALICE. • Detector prototypes have been tested with GASSIPLEX0.7-3 [4] signal processing chip which has an extended dynamic range but reduced sensitivity compared to the old chip used in tests of the prototypes described in the TDR. The MANAS chip [5], to be used in the actual case, has specifications very close to GASSIPLEX0.7-3. • A PMD having the same design as described in the TDR and with 24 supermodules having a total of about 82K readout channels has been assembled for the STAR experiment at RHIC [2]. The

6

1

Introduction

signal processing for this PMD is done by GASSIPLEX0.7-3. • A detailed study of the possibilities and limitations of search for disoriented chiral condensates using the PMD and a charged particle multiplicity detector has been carried out [6]. • Using the event plane provided by the PMD it has been shown that one can study anisotropy in the production of J/Ψ particles in the Dimuon spectrometer [7]. • A scaling relation has been proposed to deduce anisotropy in neutral pions from the measured anisotropy of photons [8]. This relation depends only on an experimentally measurable quantity χ and has a single functional form for both orders of flow. • Investigations such as a fluctuation measure as a signal for DCC, effect of limited acceptance and the role of centrality selection for fluctuation studies have been carried out [9–11].

7

2 Modifications in detector design The honeycomb gas proportional counter with extended cathode design presented in the TDR [1] remains a unique detector for preshower applications. It has a copper honeycomb as cathode kept at high negative voltage and a gold-plated tungsten wire at ground potential as anode in the center of each hexagonal cell. The cathode is extended onto the printed circuit boards (PCBs) covering the honeycomb. The design modifications presented in this chapter concern the cell cross-section, cell depth and cathode-anode distance. The cell cross-section and depth have been fixed from GEANT simulation studies.

2.1 Prototype fabrication and tests The prototypes were fabricated in the form of a honeycomb of 16 rows and 16 columns of hexagonal cells of 0.22 cm2 area each (length of one side of the hexagon being 2.85 mm). The depth of the cells was 5 mm. They were made of copper and the wall thickness of the cells was 0.4 mm as in the TDR design. The honeycomb was coated with graphite paint. Cross-sections of a unit cell of the new set of prototypes are shown in Fig. 2.1. While the basic geometry of the honeycomb cells were identical, cathode extensions on the inner part of the printed circuit boards (PCBs) covering the honeycomb were different in various cases, as shown by the sizes of the insulation circle and of the wire support. These are listed in Table 2.1 extended portion of cathode

Cathode

b

anode a

5 mm

Insulation circle

wire support

Figure 2.1: A schematic diagram of the cross section of a unit cell. ’a’ and ’b’ denote the diameters of the insulation circle and the wire support as shown.

Table 2.1: Parameters of extended cathodes for different prototypes Insulation circle dia. 4 mm 3 mm 2 mm

Wire support dia 0.5 mm 0.5 mm 0.3 mm

Reference Prototype-4 Prototype-3 Prototype-2

Testing period May 2001 Sept. 2001 June 2002

The difference in the radius of the insulation circle and the wire support denotes the minimum cathode-anode distance on the PCBs. The insulation circle having 4 mm diameter is identical with the

8

2

Modifications in detector design

140 cms CSC-3 SC-3, 4

55 cms

PMD    3 mm finger   

CSC-2

73 cms

CSC-1 SC-1, 2 Beam

279 cms

Figure 2.2: Test setup at the PS T10 beam-line during May-June 2001 for the study of charged particle response. Similar setup was used in 2002.

TDR design. It was planned to start with this cathode design and then gradually reduce the diameter of the insulation circle to values technically feasible during the fabrication of the PCBs untill the efficiency of the detector became acceptably uniform throughout the volume. As the signal was expected to be small due to reduction in cell depth, we used the old and more sensitive (1.5 µm) version of the GASSIPLEX [2] front-end electronics for signal processing in the early tests in 2001. For other tests in 2001 and for all the tests in 2002 we used the recent (0.7µm) version of the chip [3], which has specifications almost identical to those of the MANAS chip [4] to be finally used in the readout of the PMD. The test setup is shown in Fig. 2.2. A special trigger scintillator of cross-section 3 mm×3 mm was assembled. This scintillator could be positioned to cover the central part of one cell. Using two pairs of trigger scintillators (SC1-SC2 and SC3-SC4) available at the T10 beam line which had an overlap area of 1 cm2 and small finger scintillator, we used a 5-fold coincidence for selecting the central zone of the cells of the new prototype for part of the studies. To study the variation of efficiency within a cell, the small trigger scintillator was taken out of coincidence and only 4-fold coincidence was used. Tracking was provided by a set of cathode strip chambers (CSCs) as shown in the figure. For preshower studies a gas Cerenkov detector was placed between the PMD prototype and the upstream tracking chambers and the downstream components moved further as required. The trigger scintillator SC3-SC4 was moved in front of the prototype detector.

2.2 Results for charged particle detection The response of the detector to charged particles was studied using a 5 GeV/c pion beam. The results for prototype-4 and prototype-3, tested in 2001, have been described in Ref. [5]. Here we shall present only the results of prototype-2 tested in 2002. Prototype-2 showed better results in terms of efficiency and uniformity within a cell compared to the other two prototypes because the cathode is extended very close to the anode which results in improved charge collection. The operating gas mixture of Ar +CO2 in 70:30 ratio, as discussed in the TDR, has been used throughout.

2.2.1 Pulse height spectra and operating parameters A typical pulse height spectrum for 5 GeV/c pion beam incident on the prototype detector is shown in Fig 2.3(a) along with a fit to a Landau distribution. Fig 2.3(b) gives the average cluster size due to pion

9

Counts

Results for charged particle detection

Counts

2.2

800

Mean RMS

10000

1.078 0.2773

1450 V

600

7500

peak = 47 400

5000

(a)

200

0

0

200

400

(b)

2500

0

600

ADC

1

2

3

4

5

Number of cells

Figure 2.3: (a) Pulse height spectrum for 5 GeV/c pions as observed in prototype-2 operating at 1450 V, (b) Average cluster size due to 5 GeV/c pions.

100

150

95

125

Peak pulse height (ADC)

Efficiency (%)

hits. The average value being close to unity suggests that the charged particle signal is confined to one cell, satisfying one of the basic requirements of the detector.

90

85

80

(a) 75

70

100

75

50

(b) 25

1300

1400

1500

Voltage (volts)

1600

0

1300

1400

1500

Voltage (volts)

1600

Figure 2.4: (a) Efficiency and (b) peak ADC as a function of operating voltage for prototype-2. Error bars are statistical.

Fig. 2.4 shows the efficiency and the peak pulse height for a set of operating voltages. The efficiency has been calculated by (a) using the 5-fold coincidence where the small scintillator selected the central zone of the cell and (b) using 4-fold coincidence (without using the finger scintillator) and tracking to select the central part. The values denote the average efficiency in the central part of the cell. The two values agree to within a few percent. The plateau starts at 1400 V. The operating voltage in the range 1400 V to 1500 V corresponds to proportional region. The gas gain varies from about 5×10 3 to 1.2×104 in this operating region.

10

2

Modifications in detector design

2.2.2 Variation of efficiency within a cell

Efficiency (%)

The efficiency of charged particle detection at different points inside the cell was estimated by tracking the pion beams using the CSCs. Hits on the three pairs of the CSCs provided the external reference with three pairs of x and y coordinates. A linear fit passing through these three points was used to obtain the projected hits on the PMD plane. This allowed us to calculate the efficiency within smaller bins and to study its variation within the cell. Fig. 2.5 shows the efficiency as a function of x-position with a bin size of 1.5 mm. The bin is slided by 0.5 mm to obtain more data points within a cell. The origin of x-axis has been adjusted to correspond to the center of the cell. The figure suggests that while the efficiency in the central part of the detector is high and similar to that given in Fig. 2.4, it decreases near the boundary. This decrease may be attributed to the insensitive area which arises due to the thickness of the cell wall. This is verified by GEANT simulation results, which are superimposed in the figure. This also shows dips at regular intervals of cell size as in test data. The apparently higher value of efficiency near the dips in the test data arises due to large beam emittance which results in particles traveling at nonnormal incidence entering the sensitive volume after traversing the wall. GEANT simulation is done for normal incidence only. The average efficiency within a cell of the new prototype is 95.8% as compared to the TDR value of 97.6%.

110

100

90

80

70

Data Simulation

60

50

-6

-4

-2

0

2

4

6

x-position (mm) Figure 2.5: Variation of efficiency as a function of x-position (in mm) within a cell. Bin size is 1.5 mm. The origin of x-axis has been adjusted to match with the centre of the cell.

2.2.3 Relative gains of cells A number of cells have been scanned to study the relative variation in the gain. Fig 2.6 shows the relative gains for 27 cells scanned randomly around the prototype. The present prototype shows a relative gain variation of 8%, which is slightly larger than that of the prototype described in the TDR. This value is still less than 10% obtained in the case of WA98 PMD [7] where relative gains were appropriately taken

2.3

Preshower characteristics

11

Counts

care of in the offline analysis.

10

Entries RMS

27 0.8048E-01

8

6

4

2

0

0.6

0.8

1 1.2 Relative gain

1.4

Figure 2.6: Relative gains of various cells in the prototype.

2.3 Preshower characteristics Preshower characteristics have been studied for the prototype-4 using 2-4 GeV/c electron beam passing through a 3 X0 thick lead converter plate placed in front of the prototype. The trigger consisted of a three fold coincidence between a pair of scintillators and a Cerenkov counter [5].

Table 2.2: Average transverse size of preshower (in units of cells) for various electron energies and comparison with GEANT simulations. Converter thickness is 3 X0 .

Energy (GeV) 2 3 4

Data 5.0 6.5 7.6

GEANT 5.2 6.2 6.8

A connected region of hit cells above the noise threshold represents the transverse size of the preshower. The transverse preshower size for a typical case is shown in Fig. 2.7. Table 2.2 presents a comparison of average transverse shower size for the test data with GEANT simulation for various electron energies. The values are comparable, that of data being somewhat higher. This shows that a slight decrease in efficiency at the cell boundaries does not have any effect on the preshower operation of the detector. As the charged particle detection efficiencies are high in all cases, preshower operation of the other prototypes will also be comparable to GEANT simulations.

2

Counts

12

ID Entries Mean RMS

Modifications in detector design

1000000 9776 6.538 3.476

1000

500

0

0

5

10

15

20

25

Cluster size ( number of cells)

Figure 2.7: Transverse shower spread in prototype-4 for 3 GeV/c electrons passing through a 3 X 0 thick lead converter.

2.4 Behaviour at high particle flux The PMD in the new location will be required to handle substantially higher flux than in the TDR case. Whereas the capability to handle primary particle flux up to 1000/cm 2 /sec seems adequate for lead-lead and pp runs even in the new location, the flux in the case of high luminosity Ar-Ar operation of the LHC will be substantially higher (see section 1.3.3). The count rate capability of the modified detector has been studied up to a flux of ∼3000/cm2 /sec using the SPS beam. Stability of the detector for flux up to ∼40000/cm2 /sec has been studied using strong radioactive source.

2.4.1 Prototype-3 using SPS beam Count rate studies were done for the prototype-3, at the SPS X5 beam line using 100 GeV/c electron beam. The incident particle flux could be varied substantially by using the collimator window. A five fold coincidence between 2 pairs of scintillators and the 3 mm finger scintillator, as described in Sec. 2, was taken as the beam trigger. Rate per 5 spills of these trigger scintillators was noted from the scaler counts. Each spill lasted for 3.5 seconds. Normalizing by the area of the finger scintillator (9 mm 2 ), the incident flux in terms of particles/cm 2 /sec was estimated. The effect of increasing flux on the efficiency of charged particle detection and on the pulse height spectrum is shown in Fig. 2.8 for an operating voltage of 1525 V. The detector was operated for a long time at a particular flux setting to check any degradation in the behavior. We observe that the efficiency of charged particle detection remains unaffected with increasing flux. It was also noted that the pulse shape remained unchanged on varying the particle flux. Similar observations for varying count rate was observed for different operating voltages.

2.4

Behaviour at high particle flux

13

100

Efficiency

90 80 70 60

Peak pulse height( ADC)

50

80

60

40

20

0.5

1

1.5

2 3

2.5

3

3.5

2

Flux (10 particles/cm /sec)

Figure 2.8: Detection efficiency and peak pulse height for 100 GeV/c electrons as a function of incident flux for prototype-3.

2.4.2 Prototype-2 using radioactive source Measurement of the anode current of a gas detector can provide indication about its ability to handle large flux. For the detector in the absence of any ionizing radiation, this measures essentially the surface leakage current. In the presence of ionizing radiation the anode current reflects the sum of surface leakage and the ionization current. In the honeycomb geometry of the PMD a small portion of FR4 dielectric, which separates the central anode wire from the cathode extension on the PCB, is exposed to the ionization charge (see Fig. 2.1). If the ionization within the cell is not dissipated fast enough, this may lead to an accumulation of charge on the dielectric. In that case the anode current will tend to increase slowly over a period of time. Prototype-2 was operated using Ar+CO 2 (70:30) gas mixture. An area of about 4 cm×3.3 cm having a matrix of 8×8 cells was illuminated with intense radiation from a 25 micro-Curie 90 Sr β-source. The distance from the source to the detector was varied in the range 1 cm to 2.5 cm. Absorption of β-rays in the top PCB of the detector was measured using a Geiger counter for near normal incidence. The flux estimate for the cell directly below the source varied from 7000/cm 2 /sec to 43000/cm2 /sec. These estimates are good to within ±20%. However the flux intercepted by the total area of the detector has not been estimated because of uncertainties in geometrical factors and varying absorption of β-rays at non-normal incidences. Two types of investigations were done by measuring the combined anode current of 64 cells : (a) variation of anode current with time for an operating voltage of 1450 V, and (b) variation of anode current with operating voltage varying upto 1600 V. Variation of anode current with time is shown in the left part of Fig. 2.9 for three values of the incident flux along with the case of no-source. The anode current is found to slowly decrease or remain

14

2

Modifications in detector design

almost unchanged with passage of time. No hint of charge accumulation is observed. Anode current has also been measured for different voltages up to 1600 V which is much beyond the operating range of 1400-1500 V for prototype-2. The results are shown in the right part of Fig. 2.9. The increase of anode current reflects the behaviour observed in Fig. 2.4, the rate of increase reflecting the onset of gas multiplication around 1400 V. No sudden change or breakdown effect is noticeable.

24

(a)

22 5

20

16

4

Anode Current(nA)

Anode Current (nA)

18

14

12

3

10 8

2

6 4 2

1 0.5

1

1.5 2 Time (hrs)

2.5

3

1000

1100

1200 1300 1400 voltage(-V)

1500

1600

Figure 2.9: Left : Variation of anode current with time for the detector operating at 1450 V for four cases : without source (triangles), with source providing flux of 7000/cm 2/sec (filled circles), 19000/cm2/sec (open circles) and 43000/cm2/sec (squares). Right : Variation of anode current with voltage for the four cases with symbols having the same meaning as in the left part.

The above investigation suggests that the detector remains generally stable at high incident flux of particles.

15

3 Detector description

3.1 Mechanical design The mechanical design of the PMD has been modified as the detector has become smaller and lighter. The size and the total weight of the detector are now reduced by almost a factor of five (Table 1.2). In addition cooling of the detector has become necessary in view of its proximity to the TPC and increase in heat dissipation per unit area. The modified design is described in this section.

3.1.1 Unit modules and supermodules The concept of unit modules and supermodules, as described in the TDR [1], has been retained for ease of handling, assembly and operation. The supermodule remains a gas-tight enclosure housing a set of unit modules. The concepts presented in the TDR about gas tightness of the supermodules and gas flow within various unit modules have been already successfully tested and implemented in the fabrication of the STAR PMD [2]. 3.1.1.1

Modified shape

The layout of the detector, including the shape of the supermodules and unit modules have been modified with the following considerations : • The supermodule boundary walls contribute to the dead space of the detector. It is advantageous to keep the number of supermodules small. • The total number of HV channels should remain large so that a sizable fraction of the detector does not become inoperable in the event of a HV breakdown in any section of the detector. • The mechanical size of the unit module should be kept reasonable such that handling and assembly operations are conveniently carried out. • All the electronics boards should have same orientation for effective convection cooling. • The inner hole of the PMD should provide sufficient clearance for the T0 detector which will be placed behind it. • The overall size should be accommodated within the limits of the baby space frame in which the PMD will be located. There should be room for servicing of the PMD electronics by clearing it out of the shadow of the V0 detector. The new layout of the detector in the split position is shown in Fig. 3.1. This consists of four supermodules in a plane, two each of one kind (described below). There are six identical unit modules in each supermodule. The number of cells in a unit module has been increased but the cells are now arranged in a manner that the unit modules are rectangular is shape. This will result in considerable simplification during fabrication and assembly. There are two types of unit modules: one having 48 rows and 96 columns (referred to as type-A) and the other having 96 rows and 48 columns (referred to as type-B). The corresponding supermodules will also be referred as type-A (top-right and bottom-left) and type-B (top-left and bottom-right). Two types of unit modules are needed to keep the same alignment for front-end electronics (FEE) boards in the entire plane of the detector. This arrangement facilitates proper

16

3

Detector description

Figure 3.1: Split view of the modified scheme of PMD showing two types of supermodules. There are four supermdoules in one plane. The top right and bottom left supermodules are of one type and the other two are of another type.

convection cooling by chilled air. The number of cells in each unit module of the present design is the same and is eight times the number of cells in the unit module of the TDR design. The inner hole is 22 cm× 20 cm. This is sufficient to accommodate the T0 detector. The PMD splits into two halves in the vertical plane to facilitate installation and servicing. 3.1.1.2

High voltage segmentation and gas tightness

In the modified scheme, it has become necessary to provide high voltage segmentation at the unit module level. Perforated polymide strips (50 µm thick) are pasted on all four sides of the unit module, so as to form an insulating barrier when these are assembled into super modules. This is shown in the left part of Fig. 3.2. Thus there will be 100 µm thick polymide between adjacent unit modules. This scheme provides segmentation of high voltage within a supermodule. The extra dead space due to this segmentation is negligible. The total number of high voltage channels is 48. Gas tightness is achieved by sealing the boundary of two unit modules using neoprene rubber strips. This is shown in the right part of Fig. 3.2. 3.1.1.3

Fabrication and assembly of unit modules and supermodules

The components of a unit module are shown in Fig. 3.3. The honeycomb of 48×96 cells is produced by joining eight sub-units of 12×48 cells which are obtained from the vendor. The sub-units are joined on a flat surface using conducting epoxy. The basic procedure for the fabrication and assembly of unit modules and supermodules remains the same as described in the TDR. Considerable experience has been gained during the fabrication of the PMD for the STAR experiment at RHIC [2]. During the assembly of supermodules of PMD for STAR experiment the SS base plate, as described in the TDR, was replaced by a 3 mm thick FR4 plate. This

3.1

Mechanical design

17

Top PCB of Unit Module

Neoprene seal Polyimide seperator with perforations

Honeycomb Cathode Bottom PCB of Unit Module

Bottom plate of Super Module

Bottom PCB of Unit Module Perforations for gas flow Honeycomb Cathode Polyimide insulator Top PCB of Unit Module

Figure 3.2: Scheme illustrating HV segmentation among unit modules. Left picture shows wrapping of polymide sheet around a unit module. Right picture shows the boundary of two unit modules and the neoprene cover for gas tightness.

Figure 3.3: Components of a unit module. (1) Top PCB, (2) 32-pin ETEC connectors, (3) edge frame providing HV isolation and gas seal, (4) honeycomb of 48×96 cells, (5) bottom PCB showing islands of insulation circles.

18

3

Detector description

Table 3.1: Input and output air temperatures within the model for various flow rates Flow rate (l/s) 0 39 39

Input temp. (◦ C) — 21 9

Output temp. (◦ C) 60 30 17.5

was done because the quality of flatness of the FR4 plate was much superior to that of the SS plate of same size. The aluminum extruded channel on the boundary of the supermodule is slightly different from the corresponding one described in the TDR or used in the STAR PMD. The profile of the extrusion is modified to accommodate the reduced thickness of the honeycomb and a keyway slot is added on top for fixing FEE board support brackets.

3.1.2 Cooling The PMD in the new location is closer to the TPC and its heat dissipation per unit area is now more than what was estimated in the design in TDR. The ALICE Collaboration has decided to make all detector units as thermally neutral. Hence cooling of the PMD is a necessity. 3.1.2.1

Chilled air cooling arrangement

To explore the feasibility for convection cooling for the PMD, a small prototype test had been carried out [3]. For good air flow in contact with the FEE boards, it is desired that all the boards are aligned in the same direction. The density of FEE boards on the PMD surface is uniform. This is further expected to help in uniform cooling and prevent the formation of hot spots. Each half of the detector plane has thin 50 mm wide aluminum side walls. A thin polythene sheet is placed across these walls so as to form an independent shallow enclosure for the front-end electronics. Zip fasteners on the sides facilitate access to FEE boards. Air ducts positioned on the top opening of these enclosures serve as entry points for forced chilled air cooling. The ducts are baffled to reduce excess vibration due to turbulence. This is schematically shown in Fig. 3.4 It is planned to optimize the flow of chilled air so that with an input temperature of 15 ◦ C, the output temperature could be maintained at 22 ◦ C, which is the ambient temperature within the ALICE magnet. This air will hence be blown into the magnet volume and not separately collected. 3.1.2.2

Quarter scale model

The feasibility of the above scheme has been tested by a quarter scale model. The heat load of a 64channel FEE Board is expected to be approximately 1 watt. This power dissipation is simulated by a set of resistors on a similar sized dummy board. Such dummy boards are fixed on a backing panel having 21 columns with the same spacing and inclination as in PMD supermodules. There are 24 FEE boards in each column. The height of this thermal mock-up is kept similar to the height of the PMD. This is shown schematically in the left part of Fig. 3.5. An enclosure is formed to contain this dummy heat load with the help of 50 mm wide Aluminum channels on the sides and a covering polythene sheet. A set of 47 LM335 type sensors is placed over the area close to resistors on the dummy FEE boards to monitor temperature at various points. The placement of sensors within the module is shown in the right part of Fig. 3.5. Cooled air from a room air conditioning unit enters into this enclosure from the top and leaves at the bottom. Provisions are made to measure air temperature at inlet and outlet and rate of air flow through the outlet.

3.1

Mechanical design

19

Section of the baffled

(a)

air duct

1

Cool air in at 15 deg C 2

4 3

  

air out at 20 deg C

(b) FEE boards

Thin plastic sheet S.S plate

Pb Alluminum side walls

1

Super module

2

Vertical gaps for air flow

Figure 3.4: Schematic illustration of cooling arrangement using chilled air. V

Chilled air blower

Vertically aligned dummy FEE boards with heat load +temp sensors

1.8m

Polythene enclosure Locations of LM335 temp. sensors

0.5m Thermal load of one FEE board (~1W) Total load ~ 440W

Figure 3.5: (left) : Schematic of the model for cooling study, (right) : placement of temperature sensors within the model.

20

3

Detector description

T (deg. C)

T (deg. C)

Results of the cooling study are summarized in Table 3.1. The flow rate was estimated from the measurement of the air velocity. Temperatures were recorded after a time sufficient to attain equilibrium. In the absence of cooling, temperature of the FEE boards soared up to 60 ◦ C within the enclosure. Due to lack of fine control on the input temperature of chilled air, data have not been taken at the proposed value of 15◦ C to be used in ALICE. It is, however, clear that one can optimize the flow rate so that with 15◦ C as input temperature, one obtains the desired output temperature in the range of 20-22 ◦ C. Fig. 3.6 shows the temperature profile at the dummy FEE boards. The figure on the left shows the results in the absence of cooling and the figure on the right shows results for the case of air flowing with 21◦ C input temperature. The y-coordinate of the model is measured from the top. Thus in the picture on the left (no cooling) the temperature increases rapidly as we go upwards. This is because of hot air moving up and further heating the boards. With air flow and cooling taking place, the temperature profile reverses the pattern, the top part being now cooler than the bottom part. It is clear that the convection cooling is able to maintain almost uniform temperature for the entire area of the FEE boards. The temperature profile suggests almost uniform cooling and absence of any hot spots. Considering the volume of air and the inlet-outlet temperature difference, it is deduced that heat exchange efficiency is close to 100%.

60 50

30 25 20

40

15

30 20

10

10

5

0 400 350 300 250 X 200 (m 150 m ) 100 50

0 0

200

400

600

800

1000

1200

1400

1600

1800

m)

Y (m

0 400 350 300 250 X 200 (m 150 m ) 100 50

0 0

200

400

600

800

1000

1200

1400

1600

1800

m)

Y (m

Figure 3.6: Temperature profile within the model enclosed in a polythene sheet: (left) for no cooling and (right) for cooling with input air at 21◦ C flowing at the rate of 39 l/s.

3.1.3 Suspension mechanism and servicing The PMD is assembled in two equal halves. Each half has independent cooling, gas supply and readout accessories. The two halves are suspended from a stainless steel I-beam and can be moved on the beam to bring them together or separate them. The support system is designed to allow both x- and zmovements. Because of their light weight, the PMD halves can be easily handled and moved around using manually operated movement controls. The manual movement is accomplished by a timing belt mechanism coupled to the roller carriage stages of the suspension brackets. The stainless steel I-beam in turn can be moved, along with the detector halves, out of the magnet hole via guide-ways attached to the extension carriage of the baby space frame. The carriage extension to the baby frame protrudes 1 m beyond magnet hole and the detector, after withdrawing out, can be lifted up to service location at ground level.

3.2

Electronics and readout

21

Figure 3.7: Connection from the anode wires to the front-end electronics for a group of 64 cells within a matrix of 4 rows and 16 columns using two 32-pin FRC connectors (expanded view).

3.1.4 Connection to front-end electronics 3.1.4.1

FRC connector on the detector

The signal from the anode wires of 32 cells (in 4 rows and 8 columns) are grouped into one connector. This is shown in Fig. 3.7. Two such connectors are joined together by a flexible kapton cable which merges into an FEE board.

3.1.4.2

PC-bus

All the FEE boards in one row in a supermodule, encompassing all the unit modules, are connected to a single long PCB which provides mechanical support to the FEE boards, supplies low voltage power to the boards and also carries all the data and control signals between the MARC chips [4] and the digital signal processor (DSP) boards. This PCB will be referred as the PC-bus. This arrangement is schematically shown in Fig. 3.8. For type-A supermodules there are 9 FEE boards in one PC-bus and for type-B supermodules there are 12 FEE boards in one PC-bus.

3.2 Electronics and readout The front-end electronics for signal processing, digitization and readout will be based on the design concepts evolved for the tracking chambers of the Dimuon Spectrometer [4, 5]. A close collaboration with the Orsay group, which is responsible for the implementation of the electronics for the tracking chambers, will be maintained. The analog signals will be processed using the MANAS chip [4]. The digitized signal will be handled using the MARC chip [4]. Circuitry for the MANU daughter board (referred henceforth as FEE board) has been obtained from Orsay group. The layout of the printed circuit board has been adapted to the mechanical and space restrictions for the PMD. The conceptual readout chain is shown in Fig. 3.9. Various components are described in the following sections.

3.2.1 MANAS chip The MANAS chip for analog signal processing has been developed by the SINP group in India [4]. The chip has become available in plastic packaging. The test results about the linearity, dynamic range and channel-to-channel gain variation for negative input as required for the PMD are shown in Fig. 3.10. The gain is approx. 4 mV/fC and the dynamic range extends up to about 300 fC.

22

3

Detector description

l kkl '('('(' 11 2 11.-.- 2 11.-.- 211.-.- , 2 + 8 + 87 * ) ,+,+ *) ' % ts & % ts & % &% '( '       2 / 2 / 2 >== >==