The COMPASS experiment at the SPS accelerator at CERN uses a large scale Ring
Imaging CHerenkov detector (RICH) to identify pions, kaons and protons in a
wide momentum range. For the data taking in 2006, the COMPASS RICH has been
upgraded in the central photon detection area (25% of the surface) with a new
technology to detect Cherenkov photons at very high count rates of several 10^6
per second and channel and a new dead-time free read-out system, which allows
trigger rates up to 100 kHz. The Cherenkov photons are detected by an array of
576 visible and ultra-violet sensitive multi-anode photomultipliers with 16
channels each. The upgraded detector showed an excellent performance during the
2006 data taking.Comment: Proceeding of the IPRD06 conference (Siena, Okt. 06

A. Bressan

A. Ferrero

A. Lehmann

A. Maggiora

A. Magnon

A. Mann

A. Martin

A. Mutter

A. Teufel

Albrecht

B. Gobbo

B. Ketzer

C. Schill

D. Faso

D. Kramer

D. Neyret

D. Panzieri

D. von Harrach

E. Delagnes

E. Rocco

F. Bradainante

F. Kunne

F. Nerling

F. Robinet

F. Sozzi

F. Tessarotto

F.H. Heinsius

Fischer

G. Menon

G. Pesaro

H. Angerer

H. Deschamps

H. Fischer

H. Wollny

I. Konorov

J. Polak

K. Königsmann

L. Busso

L. Silva

L. Steiger

M. Alekseev

M. Apollonio

M. Chiosso

M. Finger

M. Giorgi

M. Slunecka

M. Sulc

M. Svec

M.L. Colantoni

N. Dibiase

O. Nähle

P. Abbon

P. Bordalo

P. Ciliberti

P. Pagano

P. Rebourgeard

P. Schiavon

R. Birsa

R. Hagemann

R. Joosten

S. Costa

S. Dalla Torre

S. Gerassimov

S. Levorato

S. Panebianco

S. Paul

Santiard

Schmitt

T. Dafni

V. Diaz

V. Duic

V.N. Kolosov

W. Eyrich

W. Schröder

English

arXiv

ABBON P

ALEKSEEV M

ANGERER H

APOLLONIO M

BIRSA R

BORDALO P

BUSSO L

CHIOSSO M

COLANTONI M. L

COSTA S

DALLA TORRE S

DAFNI T

DELAGNES E

DESCHAMPS H

DIAZ V

DIBIASE N

DUIC V

EYRICH W

FASO D

FERRERO A

FINGER M

FINGER M. JR

FISCHER H

GERASSIMOV S

GOBBO B

HAGEMANN R

VON HARRACH D

HEINSIUS F. H

JOOSTEN R

KETZER B

KÖNIGSMANN K

KOLOSOV V. N

KONOROV I

KRAMER D

KUNNE F

LEHMANN A

MAGGIORA A

MAGNON A

MANN A

MENON G

MUTTER A

NÄHLE O

NERLING F

NEYRET D

PAGANO P

PANEBIANCO S

PANZIERI D

PAUL S

PESARO G

POLAK J

REBOURGEARD P

ROBINET F

ROCCO E

SCHILL C

SCHRÖDER W

SILVA L

SLUNECKA M

SOZZI F

STEIGER L

SULC M

SVEC M

TESSAROTTO F

TEUFEL A

WOLLNY H.

BRADAMANTE, FRANCO

BRESSAN, Andrea

CILIBERTI, PIERO

GIORGI, MARCELLO

LEVORATO, STEFANO

MARTIN, ANNA

SCHIAVON, PAOLO

Archivio istituzionale della ricerca - Università di Trieste

Fast photon detection for the COMPASS RICH detector

Crossref

The COMPASS experiment at the SPS accelerator at CERN uses a large scale Ring Imaging CHerenkov detector (RICH) to identify pions, kaons and protons in a wide momentum range. For the data taking in 2006, the COMPASS RICH has been upgraded in the central photon detection area (25% of the surface) with a new technology to detect Cherenkov photons at very high count rates of several 10^6 per second and channel and a new dead-time free read-out system, which allows trigger rates up to 100 kHz. The Cherenkov photons are detected by an array of 576 visible and ultra-violet sensitive multi-anode photomultipliers with 16 channels each. The upgraded detector showed an excellent performance during the 2006 data taking.Particle identification at high rates is a central aspect of many present and future experiments in high-energy particle physics. The COMPASS experiment at the SPS accelerator at CERN uses a large scale Ring Imaging CHerenkov detector (RICH) to identify pions, kaons and protons in a wide momentum range. For the data taking in 2006, the COMPASS RICH has been upgraded in the central photon detection area (25% of the surface) with a new technology to detect Cherenkov photons at very high count rates of several 106s−1 per channel and a new dead-time free read-out system, which allows trigger rates up to 100 kHz. The Cherenkov photons are detected by an array of 576 visible and ultra-violet sensitive multi-anode photomultipliers with 16 channels each. Lens telescopes of fused silica lenses have been designed and built to focus the Cherenkov photons onto the individual photomultipliers. The read-out electronics of the PMTs is based on the MAD4 amplifier-discriminator chip and the dead-time free high resolution F1-TDC. The 120 ps time resolution of the digital card guarantees negligible background from uncorrelated physical events. In the outer part of the detector, where the particle rates are lower, the present multi-wire proportional chambers (MWPC) with Cesium Iodide photo-cathodes have been upgraded with a new read-out electronic system based on the APV preamplifier and shaper ASIC with analog pipeline and sampling ADCs. The project was fully designed and implemented in the period November 2004 until May 2006. The upgraded detector showed an excellent performance during the 2006 data taking: the number of detected Cherenkov photons per ring was increased from 14 to above 60 at saturation. The time resolution was improved from about 3 microseconds to about one nanosecond which allows an excellent suppression of the background photons from uncorrelated events.The COMPASS experiment at the SPS accelerator at CERN uses a large scale Ring Imaging CHerenkov detector (RICH) to identify pions, kaons and protons in a wide momentum range. For the data taking in 2006, the COMPASS RICH has been upgraded in the central photon detection area (25% of the surface) with a new technology to detect Cherenkov photons at very high count rates of several 10^6 per second and channel and a new dead-time free read-out system, which allows trigger rates up to 100 kHz. The Cherenkov photons are detected by an array of 576 visible and ultra-violet sensitive multi-anode photomultipliers with 16 channels each. The upgraded detector showed an excellent performance during the 2006 data taking

Abbon, P.

Alekseev, M.

Angerer, H.

Apollonio, M.

Birsa, R.

Bordalo, P.

Bradamante, F.

Bressan, A.

Busso, L.

Chiosso, M.

Ciliberti, P.

Colantoni, M.L.

Costa, S.

Dalla Torred, S.

Dafni, T.

Delagnes, E.

Deschamps, H.

Diaz, V.

Dibiase, N.

Duic, V.

Eyrich, W.

Faso, D.

Ferrero, A.

Finger, M.

Finger, M., Jr.

Fischer, H.

Gerassimov, S.

Giorgi, M.

Gobbo, B.

Hagemann, R.

von Harrach, D.

Heinsius, F.H.

Joosten, R.

Ketzer, B.

Konigsmann, Kay

Kolosov, V.N.

Konorov, I.

Kramer, D.

Kunnne, F.

Magnon, A.

Mann, A.

Martin, A.

Menon, G.

Mutter, A.

Nahle, O.

Nerling, F.

Neyret, D.

Pagano, P.

Panebianco, S.

arXiv:physics/0611129 v1   14 Nov 2006 Fast photon detection for the COMPASS RICH detectorP.Abbona, M.Alekseevb, H.Angererc, M.Apolloniod, R.Birsad, P.Bordaloe, F.Bradamanted, A.Bressand,L.Bussob, M.Chiossob, P.Cilibertid, M.L.Colantonif , S.Costab, S.Dalla Torred, T.Dafnia, E.Delagnesa,H.Deschampsa, V.Diazd, N.Dibiaseb, V.Duicd, W.Eyrichg, D.Fasob, A.Ferrerob, M.Fingerh, M.FingerJrh, H.Fischeri, S.Gerassimovc, M.Giorgid, B.Gobbod, R.Hagemanni, D.von Harrachj, F.H.Heinsiusi,R.Joostenk, B.Ketzerc, K.Ko¨nigsmanni, V.N.Kolosovl ∗, I.Konorovc, D.Kramerm, F.Kunnea,A.Lehmanng, S.Levoratod, A.Maggiorab, A.Magnona, A.Mannc, A.Martind, G.Menond, A.Mutteri,O.Na¨hlek, F.Nerlingi, D.Neyreta, P.Paganod, S.Panebiancoa, D.Panzierif , S.Paulc, G.Pesarod, J.Polakm, P.Rebourgearda, F.Robineta, E.Roccod, P.Schiavond, C.Schilli †, W.Schro¨derg, L.Silvae,M.Sluneckah, F.Sozzid, L.Steigerh, M.Sulcm, M.Svecm, F.Tessarottod, A.Teufelg, H.WollnyiaCEA Saclay, DSM/DAPNIA, Gif-sur-Yvette, FrancebINFN, Sezione di Torino and University of Torino, Torino, ItalycTechnische Universita¨t Mu¨nchen, Physik Department, Garching, GermanydINFN, Sezione di Trieste and University of Trieste, Trieste, ItalyeLIP, Lisbon, PortugalfINFN, Sezione di Torino and University of East Piemonte, Alessandria, ItalygUniversita¨t Erlangen-Nu¨rnberg, Physikalisches Institut, Erlangen, GermanyhCharles University, Prague, Czech Republic and JINR, Dubna, RussiaiUniversita¨t Freiburg, Physikalisches Institut, Freiburg, GermanyjUniversita¨t Mainz, Institut fu¨r Kernphysik, Mainz, GermanykUniversita¨t Bonn, Helmholtz-Institut fu¨r Strahlen- und Kernphysik, Bonn, GermanylCERN, European Organization for Nuclear Research, Geneva, SwitzerlandmTechnical University of Liberec, Liberec, Czech RepublicParticle identification at high rates is a central aspect of many present and future experiments in high-energyparticle physics. The COMPASS experiment at the SPS accelerator at CERN uses a large scale Ring ImagingCHerenkov detector (RICH) to identify pions, kaons and protons in a wide momentum range. For the data takingin 2006, the COMPASS RICH has been upgraded in the central photon detection area (25% of the surface) witha new technology to detect Cherenkov photons at very high count rates of several 106s−1 per channel and a newdead-time free read-out system, which allows trigger rates up to 100 kHz. The Cherenkov photons are detectedby an array of 576 visible and ultra-violet sensitive multi-anode photomultipliers with 16 channels each. Lenstelescopes of fused silica lenses have been designed and built to focus the Cherenkov photons onto the individualphotomultipliers. The read-out electronics of the PMTs is based on the MAD4 amplifier-discriminator chip andthe dead-time free high resolution F1-TDC. The 120 ps time resolution of the digital card guarantees negligiblebackground from uncorrelated physical events. In the outer part of the detector, where the particle rates are lower,the present multi-wire proportional chambers (MWPC) with Cesium Iodide photo-cathodes have been upgradedwith a new read-out electronic system based on the APV preamplifier and shaper ASIC with analog pipeline andsampling ADCs. The project was fully designed and implemented in the period November 2004 until May 2006.The upgraded detector showed an excellent performance during the 2006 data taking: the number of detectedCherenkov photons per ring was increased from 14 to above 60 at saturation. The time resolution was improvedfrom about 3 microseconds to about one nanosecond which allows an excellent suppression of the backgroundphotons from uncorrelated events.Keywords: COMPASS, RICH, particle identifica-∗On leave from IHEP Protvino, Russia.†Corresponding author, mail: Christian.Schill@cern.chtion, multi-anode photomultiplier tubes.PACS: 20.40.Ka, 42.79.Pw, 85.60.Gz121. IntroductionThe COMPASS experiment [1] at the CERNSPS investigates key issues in hadron physicsby scattering high-energy polarized muons andhadrons off polarized and unpolarized solid statetargets. The produced particles are detected in alarge size two-stage forward spectrometer whichcovers a wide kinematic range (10−5 < xBj < 0.5,10−3 < Q2 < 100 (GeV/c)2). One of the keyfeatures of the COMPASS spectrometer is an ex-cellent particle identification which allows to se-parate scattered electrons, muons, pions, kaonsand protons. It is performed by electromagneticand hadron calorimeters, muon walls and a largescale Ring Imaging Cherenkov detector (RICH)[2]. The RICH detector uses C4F10 as radia-tor gas inside a 5 × 6 m2 wide and 3 meterdeep vessel. The produced Cherenkov photonsare reflected by a 20 m2 mirror wall onto a setof photon-detectors: up to 2004 multi-wire pro-portional chambers (MWPC) with Cesium Iodidephoto-cathodes, covering a total active surface ofabout 5.5 m2 and including in total about 80.000read-out channels.2. Motivation of the upgradeThe read-out system of the COMPASS RICHphoton detectors in use till 2004 consisted of Gas-siplex front-end chips [3] connected to the MW-PCs, which have an integration time of about3 microseconds. In the experimental environmentof the COMPASS setup there is a large flux ofCherenkov photons especially in the centre of thedetector, since the CERN muon beam is accom-panied by 10% to 20% of halo muons which passthrough the detector and create Cherenkov rings.At high beam intensities of 0.4 to 1.0×108 muonsper second, these halo rings create a considerablebackground of overlapping rings in the centre ofthe detector, which reduces the particle identifica-tion efficiency and purity, especially for particlesin the very forward direction.A fast detection system for Cherenkov pho-tons is needed to distinguish by time informationthe photons originating from scattered particlesin the physics events from the background fromFigure 1. Lower half of the COMPASS RICHphoton detector before installation. The centralpart (marked by the white line) of the MWPCshas been replaced by lens telescopes, MAPMTsand fast read-out electronics consisting of MAD4discriminators and F1 TDC.uncorrelated halo muons. The upgrade of theCOMPASS RICH detector consists of two parts.In the central part of the detector (25% of thesensitive area) where the photon flux is largestthe MWPCs with Cesium Iodide photo-cathodeshave been replaced by multi-anode photomulti-pliers [4] and a fast read-out system based on theMAD4 [5] discriminator front-end chip and thedead-time free F1 TDC [6] (see Fig. 1). In theouter part, the existing MWPC chambers havebeen equipped with a faster read-out based onthe APV preamplifier with sampling ADCs [7].In addition, the upgraded detector allows a highrate operation at increased trigger rates from 20up to 100 kHz and small dead-time [8].3. The upgrade of the central regionThe central region upgrade is performed by re-placing the central part of the MWPC photondetector set by an array of 576 UV-sensitive 16channel multi-anode PMTs H7600-03-M16 fromHamamatsu [4]. The sensitive wavelength rangeof these photomultipliers extends from 200 nmup to 700 nm compared to the effective sensi-tive range of the Cesium-Iodide photo-cathodesof 160 nm to 200 nm. Therefore the number of3Figure 2. Optical arrangement of the MAPMTand the fused silica lens telescope.detected photons per ring is expected to be about4 times larger. In addition, the ring resolution isimproved by the larger number of detected pho-tons from 0.6 to 0.3 mrad. This will increase theupper limit of the kinematic region of the 2σ pionfrom kaon separation from 44 to above 50 GeV/chadron momentum.The Cherenkov photons are focused onto thePMTs by 576 individual lens telescopes from UV-transparent fused silica lenses (see Fig. 2). Thetelescopes have been customly designed from onespherical and one aspherical lens and offer a largeangular acceptance for the photons of±9.5o and aminimum image distortion. The image reductionis of a factor of about 7 in area; the PMT pixelsare of 4.5 × 4.5 mm2, the effective pixel size ofthe new detector is 12× 12 mm2. All PMTs havebeen shielded by soft iron boxes to protect themfrom the residual 200 Gauss field of the 1 Teslaopen spectrometer magnet few meters away.The PMTs are read out by frontend electronicsmounted directly on the detector, which consistsof the MAD4 preamplifier and discriminator andthe F1 TDC chip. The MAD4 chip [5] has a lownoise level of 5 − 7 fC compared to the averagePMT signal of about 500 fC. It is able to handlesignals up to 1 MHz rate. In 2007, the MAD4 willbe replaced by C-MAD chips, which have a ratecapability up to 5 MHz. The digital part of theread-out consists of the dead-time free F1 TDC [6]mounted on the DREISAM3 frontend card. It has3Digital REad-out Integrating and SAMpling card.Figure 3. Single physics event in the RICH de-tector, central region, after applying a time cutof 5 ns around the physics trigger. One can seeCherenkov rings of several hadrons.a time resolution of better than 120 ps and canhandle input rates up to 10 MHz at trigger ratesof up to 100 kHz. The data from one frontendcard with 64 read-out channels are transferred viaoptical links to the COMPASS read-out system[8]. All read-out electronics is mounted in a verycompact setup directly on the detector.4. Detector performance after the upgradeIn the COMPASS beam-time 2006, all datahave been taken with the upgraded RICH detec-tor (see Figs. 3, 4 and 5). The detector shows ex-cellent performance: the number of photons perring has increased from 14 before the upgrade toabove 60 at saturation (β ≈ 1). The increasedstatistics in the number of photons has improvedthe ring resolution to 0.3 mrad from 0.6 mradbefore. While the increased number of photonshas improved the particle identification capabil-ity at lower momenta, the better ring resolutionextends the particle identification towards highermomenta. The time resolution for single photons(see Fig. 4) is about 1 ns, which allows an al-most complete rejection of the background fromuncorrelated halo muon Cherenkov signals.4Figure 4. Time distribution of the Cherenkovphotons relative to the physics trigger. One cansee an excellent time resolution of about 1 ns.5. ConclusionsA fast photon detection system with multi-anode photomultipliers and fast read-out elec-tronics based on the MAD4 discriminator andthe F1 TDC has been designed and constructedto upgrade the Ring Imaging Cerenkov (RICH)detector of the COMPASS experiment. The up-graded detector was ready for the beam-time in2006 and first data show an excellent performanceof the new photon detection system. The time re-solution of about 1 ns allows an almost completerejection of the background Cherenkov photonsfrom uncorrelated muon halo events, which im-proves efficiency and purity (see Fig. 5) of theparticle identification especially in the very for-ward direction. The increased number of detectedphotons extends the particle identification per-formance of the COMPASS RICH both towardslower Cherenkov angles and at high particle mo-menta above 50 GeV/c.AcknowledgmentsWe acknowledge support from the CERN/PHgroups PH/TA1, TA2, DT2, TS/SU, and sup-Figure 5. RICH-reconstructed kaon mass-peakbefore (2004 data) and after (preliminary 2006data) the RICH upgrade.port by the BMBF (Germany) and the EuropeanCommunity-research Infrastructure Activity un-der the FP6 program (Hadron Physics, RII3-CT-2004-506078).REFERENCES1. The COMPASS Collaboration, Proposal,CERN/SPSLC 96-14 and 96-30, 297 (1996).2. E. Albrecht et al., Nucl. Instr. Meth. A 553,215-219 (2005).3. C. Santiard et al., Proc. 6th Pisa Meeting onAdvanced Detectors, La Biodola, Italy, May1994, Phys. Rev. C52, 2072 (1995).4. P. Abbon et al., Fast photon detection forCOMPASS RICH-1, accepted for publ. inNucl. Inst. Meth. A.5. F. Gonnella and M. Pegoraro, CERN-LHCC-2001-034, 204-8 (2001).6. H. Fischer et al., Nucl. Instr. Meth. A 461,507-510 (2001).7. D. Neyret et al., 4th Intern. Conf. on NewDevelopments in Photondetection, Beaune,France (2005).8. L. Schmitt et al., IEEE Trans. Nucl. Sci. 51,439 (2004).

Fast photon detection for the COMPASS RICH detector

Abstract

Similar works

Full text

Available Versions

Archivio istituzionale della ricerca - Università di Trieste

Crossref

CERN Document Server