PID meeting @Nagoya Univ. 31.Aug.2002
Contents1. Introduction2. PMT structure & Set up3. Basic performance4. Experiment results
– Gain– Time resolution
5. Summary
R&D on Fine-mesh multi-anode PMT
with T.T.S.=100 ps under B1TT.HokuueNagoya University, Japan
Fine-mesh PMTL24 -
Multi-anode
PID meeting @Nagoya Univ. 31.Aug.2002
IntroductionTOP counter : a new type of Cherenkov Ring Imaging detector
Single-photon sensitive with high efficiency Position sensitive : x 1 mm
Operate under magnetic field : B = 1.5T(at Belle )
Linear-array Multi-anode Fine-mesh PMT Nucl. Instrum. Meth. : A460,326-335,2001.
Hybrid Avalanche PhotoDiode (HAPD) Nucl. Instrum. Meth. : A463,220-226,2001.
Transit time spread : TTS = 100 ps
Our candidates
Requirements
PID meeting @Nagoya Univ. 31.Aug.2002
A fine-mesh PMT exhibits a good position resolution and moderate time resolution for high multiple-photons, but not for single-photon.
We focused our effort to enhance the multiplication gain.
Under the magnetic field:
PID meeting @Nagoya Univ. 31.Aug.2002
PMT structures
We made 3 different fine-mesh PMTs
Base: Multi-anode Fine-mesh PMT (R6135-L24X) made by Hamamatsu Photonics Company(HPK),Japan
• Common structure : - 24 anodes (readout
channels)- anode size 26.50.8 mm- # of stages of fine-mesh dynode 24 () or 19 ()
PMT Type
Distance L (mm)
H.V divider network ratio
Mesh Size (lines/inch),pitch
- 2.5-3 1:1: :1 2000 ,12.5m- 1 2:1: :1 2000 ,12.5m- 1 2:1: :1 2500 ,9m
PID meeting @Nagoya Univ. 31.Aug.2002
1. Shorter distance between photo-cathode and first dynode2. H.V divider network ratio3. Finer mesh size
1. Shorter distance between photo-cathode and the first dynode
Transit time:
E1: the applied voltage across LL = 2.5-3 mm t 660 psL = 1 mm t 270 ps
L = 2.5-3 mmL = 1 mm
PID meeting @Nagoya Univ. 31.Aug.2002
3. Finer mesh size
2. H.V divider network ratio
T.T.S. 100 ps (1: 1: 1:1) T.T.S. 70 ps (2: 2: 1:1)(ex.) Line-forcused PMT (R5900-L16)
1:1: … :1 2:1: … :1
2000 lines/inch (12.5m pitch) 2500 lines/inch (9m pitch)
The radius reduces with field strength.• The secondary electrons would
get to hit fewer dynodes
Using the finer mesh would undo this reduction somewhat!!
reduced multiplication gain
PID meeting @Nagoya Univ. 31.Aug.2002
Set up• Set up
L24 -
PID meeting @Nagoya Univ. 31.Aug.2002
Basic performance• Signal shape (-)
1. Single-photon sensitive
B = 0.4 T , H.V = 2400 V
The exhibits a quite clear single-photon peak.
Efficiency : 52 % (-)
• ADC distributions
Rise time 1ns
63 % (-)85% (-)
PID meeting @Nagoya Univ. 31.Aug.2002
Basic performance2. Position sensitive
You can see clearly the field effect at weak field!!
- setting 1mm-wide slit on PMT’s surface• Anode-distributions(-
)• Signal spread in root-mean-square
The resolution of 0.5mm is dominated by the slit width of 1mm.True resolution might be much better than this.
PID meeting @Nagoya Univ. 31.Aug.2002
Gain • Multiplication Gain • Relative gain
The : Gain 5 10 (B = 1.5T, H.V= 3400V)6
H.V = 1600 V
The exhibits less reduction and the highest gain at 0.2T.The : Gain 8 10 (B = 1.5 T, H.V= 2000 V)5
Gain/Gain(B=0T)
PID meeting @Nagoya Univ. 31.Aug.2002
Time resolution• ADC-sliced time resolution (-,) & time-walk correction
0.4T,1.5kV 0.6T,1.7kV 1.0T,2.2kV
T.T.S 150 ps at ADC = 175-th ch at
T.T.S 100 ps at B 1T
0.4T,2.4kV
T.T.S 100 ps at ADC = 180-190 ch
-
-
150 ps at B = 1.5T
type
PID meeting @Nagoya Univ. 31.Aug.2002
• Gain vs. T.T.S.
Increment of gain by factor of 10
has rather steeper relation than
improve T.T.S of
30 ps (-)45 ps (-)
The time resolution under various conditions are plotted for and PMTs.
Both PMTs indicate that the multiplication gain of 3-5 10 are required to have a time resolution of 100ps.
7
PID meeting @Nagoya Univ. 31.Aug.2002
• Multi-photons2-photons TTS 80 ps3-photons TTS 70 ps4-photons TTS 60 ps
• T.T.S. with Multi-photons (-)
We already obtained high time resolution for multiple-photons.
PID meeting @Nagoya Univ. 31.Aug.2002
- By developing fine-mesh 24-anodes PMT
Summary
Time resolution : 100 ps (B1T)150 ps (B=1.5T)
- To have a 100 ps resolution under B=1.5T multiplication gain of
3-5 10 is required 7
- For higher gain and better T.T.S.
by using finer mesh dynodes by increasingly applied H.V. on the first dynode
- For Multiple-photons …
by reducing distance between the first dynode and photo-cathode