Upload
pekelo
View
27
Download
0
Tags:
Embed Size (px)
DESCRIPTION
The possibility of improving TOP counter. Nagoya university Yuji Enari. Introduction. mention about the p /K separation of TOP counter, especially about effect of group velocity of the photon. Definition of Separation. D TOP + D TOF. S =. ・ N ph. s t. - PowerPoint PPT Presentation
Citation preview
2002.8.31 PID meeging @ Nagoya univ 1
The possibility of improving TOP counter
Nagoya university
Yuji Enari
2002.8.31 PID meeging @ Nagoya univ 2
Introduction
• mention about the /K separation of TOP counter,
especially about effect of group velocity of the photon.
• Definition of Separation.
S = ・ Nph
TOP + TOF
t
S1ph = Separation of single photon
TOP,TOF : time difference of pi/K (K-pi)t : Time resolution
Nph : Number of detected Photo-electron
2002.8.31 PID meeging @ Nagoya univ 3
Time difference TOP and TOF
TOFTOP
TOP + TOF = 200ps
TOP counter measures time difference btw /K
2002.8.31 PID meeging @ Nagoya univ 4
Uncertainty of TOP measurement.
If we choose to use bar-TOP, this effect is negligible.
2002.8.31 PID meeging @ Nagoya univ 5
The chromatic effect.
The chromatic effect consists of 2 component.
a. Cherenkov angle Determined by the reflective index
b. Light velocity Determined by ‘Group’ index
a : b = -1 : 2 chromatic (1/n ・ n)These two contribution work oppositely.
b.
a.
2002.8.31 PID meeging @ Nagoya univ 6
The measurement of TOP resolution
• From the Beam test result.
– With improved polishing accuracy of the quartz bar.
– This result is limited by chromatic effect (at large L).
Estimate pi/K separability in the Belle detector
2002.8.31 PID meeging @ Nagoya univ 7
TOP difference and Nph in Belle detector
30° 45° 60° 90° 120° 140°
TOP : -3.6 -1.4 14.6 110.0 14.6 2.7
TOF : 62.6 44.2 36.1 31.3 36.1 40.84
Nph : ~ 90 ~ 60 ~ 40 ~ 30 ~ 40 ~ 65
P = 3.5GeV/c, barthick = 20mm
2002.8.31 PID meeging @ Nagoya univ 8
Expected TOP counter’s performance in Belle.
• Separation of single photo-electron and S
mean = 390nm, tts = 75ps
Number of detectedphoton
S1p
h
S
Hard to separate /K around in = 45, p=3.5GeV/c region.
30 45 60 90 140
2002.8.31 PID meeging @ Nagoya univ 9
How we can do?
• Increase photon statistics– Use High Q.E. material (Ga ・ As or APD?)– Use thicker quartz bar. (20mm 40mm)
• Improve time resolution.– Use long wave length region (n get small)– (and) use good photon detector(T.T.S < 50ps)
2002.8.31 PID meeging @ Nagoya univ 10
Correlation between TTS and wave length.
tts = 100ps tts = 50ps
P = 3.5GeV/c, in Belle systemSeparation of single photo-electron
S=3
S=5.5
We have to use long wave length with tts < 50 ps.
S1p
h
2002.8.31 PID meeging @ Nagoya univ 11
• wave length : peak = 490nm with high Q.E.(20%@peak) time resolution : tts=50ps
barthick = 20mm barthick = 40mm
2002.8.31 PID meeging @ Nagoya univ 12
Summary
• The chromatic effect make the largest uncertainty.
• To get good performance in Belle system,– Measure long wave length region.– Use good Photon detector which has TTS of 50 ps.– Need good Q.E. material.(Q.E.×C.E.> 20% ?)– Workable in 1.5T magnetic field
Photon detector R&D is very very important.
2002.8.31 PID meeging @ Nagoya univ 13
Silicon Photo-Multiplier
2002.8.31 PID meeging @ Nagoya univ 14
What’s SiPM
• SiPM– a kind of multi pixel Avalanche Photo Diode. – Operate in limited Geiger mode.
pixel size : 42 ×42 mm2
• Merit?– Available in magnetic field.– High Q.E. at long wave length (very at
tractive for TOP counter) ,– High gain.– Good time resolution Etc.etc.
2002.8.31 PID meeging @ Nagoya univ 15
Geiger-mode Avalanche photo diode
• Limited Geiger-mode in SiPM
– Under bias voltage of 10-20% more than break down voltage.
– Geiger discharge is stopped when bias goes down below b.d. voltage.
– Gain :• Qpixel = Cpixel ・ (Vbias – Vbeakdown)
– Cpixel 100fF Qpixel 100pC
Close up view of pixel
All pixel(576pixel) are connected by common Al strip. each pixel operates as a binary device, works as an analogue detector.
Vbias ~ 50 V
2002.8.31 PID meeging @ Nagoya univ 16
Performance of SiPM
• Pulse shape
• Gain
• Linearity and dynamic range.
• Detection efficiency
• Noise – temperature dependence.
• Time resolution
2002.8.31 PID meeging @ Nagoya univ 17
pulse height spectra
SiPM has good energy resolution as long as 2 photons enter in same pixel.
2002.8.31 PID meeging @ Nagoya univ 18
Detection efficiency
2002.8.31 PID meeging @ Nagoya univ 19
Noise
2002.8.31 PID meeging @ Nagoya univ 20
Time resolution
~ 50ps
2002.8.31 PID meeging @ Nagoya univ 21
Comparison to another detector
2002.8.31 PID meeging @ Nagoya univ 22
Summary
• SiPM is very good application for TOP counter.• High Q.E. High gain, single photon sensitive.• Good timing resolution.• Workable in strong magnetic field of 1.5T.
• To be use in TOP counter…– Size. (1mm2 20mm ×200mm?)– Enlarge the effective area in each pixel. ( = 0.3 0.5)– Noise
2002.8.31 PID meeging @ Nagoya univ 23
Reference
1, B.Dolgoshein (Moscow Engineering and Physics Institute)
- An Advanced study of Silicon Photomultiplier
ICFA instrumentation Bulletin
- The silicon photomultiplier and its possible application
transparency of 3rd BEAUNE conference
and its proceeding