1 / 19

The Vacuum Phototriodes for the CMS Electromagnetic Calorimeter P R Hobson, D C Imrie, O Sharif

The Vacuum Phototriodes for the CMS Electromagnetic Calorimeter P R Hobson, D C Imrie, O Sharif Brunel University, UK K W Bell, R M Brown , D J A Cockerill, P S Flower, B W Kennedy, A L Lintern, M Sproston, J H Williams CLRC - Rutherford Appleton Laboratory, UK

linus-deleon
Download Presentation

The Vacuum Phototriodes for the CMS Electromagnetic Calorimeter P R Hobson, D C Imrie, O Sharif

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Vacuum Phototriodes for the CMS Electromagnetic Calorimeter P R Hobson, D C Imrie, O Sharif Brunel University, UK K W Bell, R M Brown, D J A Cockerill, P S Flower, B W Kennedy, A L Lintern, M Sproston, J H Williams CLRC - Rutherford Appleton Laboratory, UK (With acknowledgements to H F Heath and colleagues at Bristol University, UK and D Seliverstov and colleagues at PNPI, Russia) HEP2001 Budapest - Hungary July 2001 HEP2001, Budapest, July 2001 R M Brown - RAL 1

  2. Outline of Talk • Overview of CMS • The Electromagnetic Calorimeter (ECAL) • Properties of Lead Tungstate • Radiation levels • VPT Performance (End cap) • APD Performance (Barrel) • Status summary HEP2001, Budapest, July 2001 R M Brown - RAL 2

  3. Compact Muon Solenoid ECAL HCAL Superconducting coil Total mass : 12,500t Overall Diameter: 15.0m Overall Length: 21.6m Magnetic field: 4T HEP2001, Budapest, July 2001 R M Brown - RAL 3

  4. ECAL design objectives Benchmark physics process: Search for ~130 GeV Higgs via H    (Sensitivity depends critically on mass resoln) m /m = 0.5[E1/E1  E2/E2  / tan(/2)] WhereE/E = a/E  b  c/E Performance Aims: BarrelEnd cap Stochastic term, a: (p.e. statistics/shower fluctuation) 2.7% 5.7% Constant term, b: (non-uniformities, shower leakage) 0.55% 0.55% Noise term, c: (Electronic noise, event pile-up) Low L 155MeV 205MeV High L210MeV 245MeV (Angular resolution limited by uncertainty in position of interaction vertex) HEP2001, Budapest, July 2001 R M Brown - RAL 4

  5. Lead Tungstate Properties • Advantages: • Fast • Dense • Radiation hard • Emission in visible • Disadvantages: • Temperature dependence • Low light yield •  Photodetector with gain • (in a strong magnetic field) HEP2001, Budapest, July 2001 R M Brown - RAL 5

  6. CMS ECAL Layout Full projective geometry (‘Off-pointing’ by 3o) Barrel: 17x2 Crystal types End cap: 1 Crystal type 1290 mm 3170 mm HEP2001, Budapest, July 2001 R M Brown - RAL 6

  7. HCAL Barrel ECAL Endcap 0.2 1.2 0.35 0.5 2 ECAL Barrel 5 3 70 20 50 Doses and neutron fluences Integrated dose (kGy) and neutron fluence (x1013 cm-2) for  L = 5x105 pb-1 (~10 yrs) Black: Dose in the Crystals at the position of the shower maximum Blue: Dose behind the crystals at the position of the photodetectors Red: Neutron fluences behind the crystals HEP2001, Budapest, July 2001 R M Brown - RAL 7

  8. =26.5 mm MESH ANODE Photodetectors: end caps • B-field orientation favourable for VPTs • (Axes: 8.5o < || < 25.5o wrt to field) • More radiation hard than Si diodes • (with UV glass window) • Gain 8 -10 at B = 4 T • Active area of ~ 280 mm2/crystal • Q.E. ~ 20% at 420 nm • Vacuum Phototriode (VPT): • Single stage photomultiplier tube with fine metal gridanode HEP2001, Budapest, July 2001 R M Brown - RAL 8

  9. VPT Gain vs Dynode Voltage HEP2001, Budapest, July 2001 R M Brown - RAL 9

  10. VACUUM PHOTOTRIODE HV FILTERING ELECTRONICS CRYSTAL ‘Supercrystal’ Layout ‘Supercrystal’: carbon-fibre alveola containing 5x5 tapered crystals + VPTs + passive HV filter (160 Identical Supercrystals per Dee) Signals fed via 600 mm cable to Preamplifier + Front End electronics behind Dee Backplate HEP2001, Budapest, July 2001 R M Brown - RAL 10

  11. Characterisation of VPTs Detail of RAL test Cell 4.0T Solenoid at Brunel 1.8T Dipole Magnet at RAL All VPTs are measured at 0  B  1.8T and -30o 30o at RAL Sample VPTs are measured at B =4.0T and  = 15o at Brunel Perspex diffuser plate with LEDs at corners. (Red circle indicates effective VPT diameter) 500 ‘Preproduction’ VPTs delivered by RIE (St Petersburg) HEP2001, Budapest, July 2001 R M Brown - RAL 11

  12. Response vs Angle at B=1.8T Arrows indicate angular regions of end caps HEP2001, Budapest, July 2001 R M Brown - RAL 12

  13. 0.80 0.85 0.90 0.95 1.00 1.05 1.10 Response vs B-Field Strength VPT Axis at 15o w.r.t. Magnetic Field HEP2001, Budapest, July 2001 R M Brown - RAL 13

  14. 6 8 10 12 14 16 18 20 16 18 20 22 24 26 28 30 (%) Distributions of Gain (B=0) and Quantum Efficiency Taken from the ‘passport’ supplied with each tube by the manufacturer Gain and quantum efficiency are uncorrelated HEP2001, Budapest, July 2001 R M Brown - RAL 14

  15. 0 10 20 30 40 50 60 70 80 90 100 Anode Response Distribution B=1.8T =15o Spread in anode response  Some sorting of VPTs necessary HEP2001, Budapest, July 2001 R M Brown - RAL 15

  16. Test beam:Energy Resolution No preshower detector With preshower detector HEP2001, Budapest, July 2001 R M Brown - RAL 16

  17. Faceplate optical transmission Post-irradiation Loss in optical transmission of 2 faceplate samples after 25 kGy 60Co irradiation (380Gy/hour) (approx 10 yrs LHC at  = 2.6) HEP2001, Budapest, July 2001 R M Brown - RAL 17

  18. VPT Behaviour Under Irradiation 60Co Irradiation (58 Gy/hr) Photocurrent produced by Cerenkov light in VPT window. (Vertical lines correspond to pauses in irradiation) VA=1000 VD= 800 HEP2001, Budapest, July 2001 R M Brown - RAL 18

  19. VPT Summary • A new generation of fine-mesh VPTs has been developed to satisfy the high magnetic field/radiation hardness requirements of CMS • An automated characterisation facility has been commissioned to handle 15000 devices • The performance of 500 pre-production VPTs from RIE meets CMS requirements HEP2001, Budapest, July 2001 R M Brown - RAL 19

More Related