1. The High Dynamics Readout of PMT for BGO Calorimeter
Calo2010. May Beijing
The High Dynamics Readout of PMT for BGO Calorimeter
Center for Particle Physics and Technology
University of Science and Technology of China
Yunlong Zhang
Calo2010. May Beijing
CPPT USTC

2. Overview Motivation Experiment Setup Results ● LED Test
Calo2010. May Beijing
Overview
Motivation
Experiment Setup
Results
● LED Test
● Cosmic Ray Test
Outlook
Calo2010. May Beijing
CPPT USTC

3. Calo2010. May Beijing
Motivation
Why would we need to design high dynamic range readout for calorimeter ？
For one cell of BGO-EM energy deposition of electron/gamma with energy above TeV is between 0.5 MIPs and 105 MIPs, the readout system need to cover this high dynamic range.
e- 300GeV
Calo2010. May Beijing
CPPT USTC

4. Experiment Setup Pulse generator LED optical fiber PMT
Calo2010. May Beijing
CPPT USTC

5. It was coupled with R5611 PMT that in the crystal bottom
Experiment Setup
BGO crystal
It was coupled with R5611 PMT that in the crystal bottom
optical fiber
XP2262B
Calo2010. May Beijing
CPPT USTC

6. Experiment Setup The block diagram for the calibration measurement.
The LED was driven by a pulse generator. The photon intensity was controlled by the voltage of the generator. The VA32 is a charged preamplifier and it’s charge range is from -4pc to 12pc.
Calo2010. May Beijing
CPPT USTC

7. The Response Function of PMT
Q1=Q0
n=0
σ1 = σ0
E.H. Bellamy. Et al., Nucl. Instr. And Method., A339(1994)
μ is the mean photoelectrons number detected by PMT.
σ1 is the single photoelectron’s sigma
Q1 is the channel of single photoelectron
Q0 is the pedestal position
σ0is the pedestal sigma
The response of a multiplicative dynode system to a single photoelectron can be discribed by a gaussian distribution
The number of detected photoelectrons in PMT cathode follow a poisson distribution.
Calo2010. May Beijing
CPPT USTC

8. Test PMT —— XP2262B channel channel Calculate gain(*106) of PMT:
μ= 1.6
1 ph.e
μ= 2.6
Q1= 339.5±9.2
2 ph.e
Q1=
3 ph.e
channel
channel
Calculate gain(*106) of PMT:
μ= 10.0
Q1= 328.1±7.3
μ= 1.6 : ±0.065
μ= 2.6 : ±0.062
μ= 10.0: ±0.052
channel
Calo2010. May Beijing
CPPT USTC

9. Test PMT — R5611
Calo2010. May Beijing
CPPT USTC

10. Test PMT — R5611
μ= 4.4
Q1 = 24.4
The gain of R5611 at high voltage 800V is (1.7±0.3)e+5.
Calo2010. May Beijing
CPPT USTC

11. Relationship Between Dynodes
Fit function: a+b*x
As the light intensity increase gradually, the signal of dynode 7 and 4 increase too.
we can see the signal of dy7 is about 20 times that of dy4.
Fit function:a+b*x+c*x2
Calo2010. May Beijing
CPPT USTC

12. The Output of Anode vs Dynode
From the experiment, we got the single photoelectron’s ADC channel of Anode is 24. We measured the relationship between anode and dynode7, finding the single photoelectron position of dy7 is 0.54 channel. According to relationship between dy7 and dy4, we noticed dy4’s single photoelectron position is channel.
Calo2010. May Beijing
CPPT USTC

13. The Output of Dynode vs LED Intensity
The intensity of LED light (ph.e) and ADC channel measured by each dynode.
Calo2010. May Beijing
CPPT USTC

14. Cosmic Ray Test The block diagram for cosmic test
Calo2010. May Beijing
CPPT USTC

15. Cosmic Ray Test Signal of Dy7: ~3000 Signal of Dy4: ~150
Calo2010. May Beijing
CPPT USTC

16. Cosmic Ray Test Dy7 Dy4 Dy1 Min(MIPs) 0.5 100 2000? Max(MIPs) 250 2500
Because of the Dy7 could only response over about 20 ph.e (or 40 channels test by LED)
So we can put an absorber between BGO and PMT to attenuate photons, ensuring the response of Dy7 to 1 MIPs is about 80 channels. So the dynamic range of Dy7 is 0.5 MIPs to 125 MIPs. According the correlation between Dynodes, we can set:
Dy7
Dy4
Dy1
Min(MIPs)
0.5
100
2000?
Max(MIPs)
250
2500
50000?
Calo2010. May Beijing
CPPT USTC

17. Outlook complete dynode readout studies Dynode 1…
continue “absorber” test
try PD or APD readout
Calo2010. May Beijing
CPPT USTC

18. Thanks
Calo2010. May Beijing
CPPT USTC