1. Performance test of a RICH with time-of-flight information
Daiji Hayashi
Nagoya Univ.
Contents
Introduction
Setup for beam test
Measurement contents
Results
Summary
My name is Daiji Hayashi, a master course student.
The title is performance test of a RICH with time-of-flight information.
At first, I introduce Aerogel RICH.
Setup for beam test, measurement contents.
At last,I will summarize my talk.

2. Introduction Proximity focusing RICH with Aerogel radiator
For upgrade of Belle detector
Kinematic region 0.7~4 GeV/c, K/π separation>4σ
Due to a limited space available →　Proximity focusing Aerogel RICH
Let me move on introduction.
Present RICH is like this illustration.
This is aerogel radiator.
This is PMT.
The principle is particle separation with Cherenkov angle theta c depending on the mass of the particle.
The particle separation power is 4 sigma at kinematic region of 0.7 to 4 GeV.
Considered to cover forward region

3. K/π separation per track : 5.0σ @ 4 GeV/c
R&D studies ; history
Multi radiator Aerogel RICH
First Aerogel RICH
RICH with TOF
(X,Y,T)
sθ : 13mrad
Npe/ring : 8.5
K/π separation per track : 4 GeV/c
sθ : 14mrad
Npe/ring : 6.4

4. Research interest
Can we improve the performance of Aerogel RICH by adding high precision timing measurement ?
RICH with TOF
(X,Y,T)
Aerogel RICH
(X,Y)

5. New type Aerogel RICH R G ⊿TOFR=42psec ⊿TOFG=47psec RICH with TOF
ΔTOF1(K-π)=42psec
⊿TOFR=42psec
(1 photon) R
Aeroｇel
⊿TOFG=47psec
(Multi photons)
4GeV G IP
1.8m
0.2m
Cherenkov photons
generate in glass
PMT
Multi anode MCP-PMT from BURLE at later can reach 19 psec for multi photons.
More than 2.4σ for multi photons?
Investigated possibility of ‘RICH with TOF’ with Beam test

6. Beam test setup Estimate time resolution of ‘RICH with TOF’
by measuring time difference between start counter.
Multi-anode MCP-PMT
BURLE R
Start counter
Aerogel
radiator R
Cherenkov photon
from aerogel
MWPC
MWPC
1.045
1.053 G
MCP-PMT
HPK R3809U G
Beam(p)
Cherenkov photon
from window
Quartz
Scintillation
trigger counter
Multi-anode MCP-PMT : Burle MCP-PMT
(13 pixels readout by KC3781A TDC(Kaizu works) via FTA820 amplifier(ORTEC))
Start counter : HPK R3809U MCP-PMT attached quartz bar on window
(TTS : s=10 psec)

7. Start counter
BURLE MCP-PMT
Trigger counter

8. 64 anode BURLE MCP-PMT BURLE 85011-501 MCP-PMT: 64(8×8) anode pads
pitch : 6.45mm, gap : 0.5mm
2 MCPs
25 mm pores
bialkali photocathode
gain : 0.6x106
collection efficiency : 60%
box dimensions : 71mm square
active area fraction : 52%
Dependence of # of detected photons
Measured by laser pulse
@ Nagoya
Expectation:
@ glass hit point(G)
Npe : 12(simulation)
Time resolution : 35 psec
@ ring image point(R)
Time resolution : 56 psec

9. Beam test measurement contents
1.Time resolution for 1 glass hit point(G).
2. Proton / p separation (G).
3. Time resolution for 1 (G)
4.Time ring image point(R).

10. Time resolution @ glass hit point(G)
Measured time resolution at the pixel hit by beam.
Parameters were adjusted with threshold scan & HV scan.
Threshold scan
@ HV=2.4kV HV
threshold=150mV
TDCBURLE-TDCSTART COUNTER
Time resolution(psec)
Time resolution(psec)
Event
Gain:0.49x106
Threshold(mV)
HV(kV)
1 photon
Pulse height
Time resolution : 34psec
TDC count(/25psec)
(Time walk corrected)

11. Proton / p separation demonstration (1)
To examine TOF capability of ‘RICH with TOF’, measured TOF of proton and p at glass hit point(G) between start counter and BURLE MCP-PMT.
Distance between start counter and Burle PMT : 65 cm
Setup
MCP-PMT
BURLE
MWPC
MWPC
MCP-PMT
HPK R3809U
ACC
Beam(p/p) G
Trigger
counter
Quartz

12. Proton / p separation demonstration (2)
Irradiated proton and p of momenta 2 GeV/c, 2.4 GeV/c, and 3.4 GeV/c.
TDCBURLE-TDCSTART 2 GeV/c
Expected DTOFp-p
and measured points p
DTOFp-p
Event p
TDC count(/25psec)
Time resolution : 38psec
Confirmed separation of proton and p with TOF.
TOF information is correctly measured.

13. Expansion of photon detection area
At glass hit point(G), not only 1 pixel but also neighboring pixels detect Cherenkov photons.
BURLE PMT pixel map
# of detected pixels
ADC mean of each pixels
Beam pass pixel
Event
Read out 13 pixels
# of pixels
Multi pixels detect Cherenkov photons for 1 track.
Can multi pixel information improve time resolution?

14. Time resolution @(G) for 1 track
Estimated time resolution which information of neighboring pixel was included.
TDC average of 5 pixels
Evaluate TDC average of neighbor 5 pixels.
Event
BURLE PMT pixel map
28psec
Beam pass pixel
TDC count(/25psec)
Time resolution for 1 track : 28psec
(Time resolution for 1 pixel : 34psec)

15. Time resolution @ ring image point(R)
Measured time ring image point(R)
Parameters : HV=2.6kV, threshold=20mV
PMT
TDCBURLE-TDCSTART COUNTER
Aerogel
Event
Time resolution for 1 pixel
: 51psec(1 photon)
TDC count(/25psec)

16. Summary 51/√Npe (Npe=6; 21psec) Separation power of TOF(R & G)
Possibility of ‘RICH with TOF’ was estimated with beam test.
Results:
Time glass hit point(G) : 34psec
Time (G) for 1 track : 28psec
Time ring image point(R) : 51psec/pe
Test with p/p beam demonstrated TOF capability.
If uncorrelate
51/√Npe (Npe=6; 21psec)
Results are consistent with expectation.
(Expectation value: Point(G) : 35psec, Point(R) : 56psec)
Separation power of TOF
(G)
Separation power of TOF(R & G)
with Burle MCP-PMT
STOF= 4GeV/c
SEPARATION POWER(s)
Aerogel threshold
MOMENTUM(GeV/c)

17. Backup
Backup slides

18. Proton / p separation with 1 pixel
Expected TOF distance
and measured points
P=+2.0GeV/c
P=+2.4GeV/c
P=+3.4GeV/c p
36psec
46psec
38psec p
41psec
38psec
37psec

19. Separation power estimation
Separation power with TOF at (R) and (G)
Total separation with TOF of (R) and (G)

20. Time walk correction
Before correction
After correction

21. Number of detected photons
adc(ch1)
~120

22. Time resolution of start counter
Measured time resolution by putting 2 identical PMTs in the beam.
Adjusted threshold value with threshold scan.
Parameters：HV=3.4kV, ATTN=30dB, Quartz 1cm
Time resolution(psec)
2ns
200mV
Start counter signal（before ADC）
1 photon
Threshold(mV)
Reason of time resolution-deterioration
Lower threshold: Small slope of signal form.
Higher threshold: Miss photons which arrive
on photocathode at early timing.
Time resolution of start counter
10.0psec

23. Set up (Circuit)

24. Circuit fluctuation
Input signal is clock signal via differential circuit.
RESULT
Circuit
HPK threshold[mV]
HPK ATTN[dB]
Burle threshold[mV]
Time resolution
[psec]
HPK-HPK
-20
W/O
8.6※1
Burle-HPK
-50 10
12.9
※1　Divided by
Circuit fluctuation of CAMAC sistem is usually 9 ~ 10 psec.

25. Analysis process At first, both p & p events are mixed.
Because protons are not detected with ACC-trigger, we can select only p events from the mixed events by cutting ADC pedestal of ACC-trigger.
Decide parameters of function for time walk correction by fitting ADC-TDC 2d distribution of p events.
Apply the parameters for both p & p events, and we can get corrected TDC distribution of both p & p events. p p p p

26. Start counter High-resolution TOF using Cherenkov light
Small-size quartz : Cherenkov light (Decay time ~ 0)
MCP-PMT : TTS < 50ps for single photon
Test counter
Num. of photo-electron ~ 260
 Time resolution = 10.6 psec
(including 8.8psec readout fluctuation)
The purpose of this study is to make a high-resolution TOF using the Cherenkov light.
To get the high resolution, we use small-size quartz and MCP-PMT. Its TTS is less than 50ps for single photon.
We tested this type of counter. Here is the result.
The obtained number of photo-electron is about 260 and the time resolution is 10.6 ps, including 8.8ps readout fluctuation.