lifetime of hpk square-shape mcp-pmt
DESCRIPTION
Lifetime of HPK Square-shape MCP-PMT. T. Mori ( Nagoya University) On behalf of Belle II PID group Dec. 1, 2010 Fast Timing Workshop Cracow , Poland. Belle & Belle-II Experiments. Super B-factory. Belle detector. Belle II experiment. K /π-ID is important Belle: 3σ. K /π-ID power: 4σ - PowerPoint PPT PresentationTRANSCRIPT
Lifetime of HPK Square-shape MCP-PMT
T. Mori (Nagoya University)On behalf of Belle II PID group
Dec. 1, 2010Fast Timing Workshop
Cracow, Poland
Belle detector3.5GeV
8GeV
Belle & Belle-II Experiments
• K/π-ID is important– Belle: 3σ
• K/π-ID power: 4σ– ex. S/N ×5 for B ππ
• High background rate
Dec. 1, 2010 Fast Timing WS, Cracow 2
Higher statistics : Higher luminosity (×~40)B-factory
Higher accuracy : Belle detector upgrade&Super B-factory
2.6m
1.2
m
e- : 7GeV
e+: 4GeV
1.5T
ForwardBackward
Install here(10cm gap of barrel part)Belle II detector cross section
Belle II experiment
TOP counterFor barrel part
(Time Of Propagation)
TOF + ACC(ACC: Threshold type Aerogel Cherenkov Counter)
TOP Counter
Dec. 1, 2010 3Fast Timing WS, Cracow
~ O(1m)
πK
⊿t ~ O(100ps)
K, π with p = 4GeV/c⊿TOP = 40ps (L ~ 1m, θ⊿ C = 6mrad)⊿TOF = 30ps (L ~ 1m)
• Time Of Propagation counter– RICH + TOF technique– Cherenkov radiator + time sensitive screen– Position (x, y) (RICH) Position + time (x, t)⇒– Very compact & simple– Radiation hardness
Performance & Important Device• Performance definition
• σphotodetector : TTS of photodetector
• Ndet: number of detected photons
Dec. 1, 2010 Fast Timing WS, Cracow 4
dettop
NTOPTOF
S
Separation power :
Photo-detector is very important
Our selection: MCP-PMT
• Requirements– TTS : <50ps– Gain : 1.0×106
• Single photon detection• Enough statistics for TTS
– QE : >20%@λ=400nm– Available in B -field
2radiator
2torphotodetectop
> ~ 50ps (Chromatic)
Square-shaped MCP-PMT: SL10
Dec. 1, 2010 5Fast Timing WS, Cracow
φ11mm 27.5mm
27.5mm
Ordinary cylindrical MCP-PMT
SquareMCP-PMT
Co-development withHamamatsu Photonics K.K.
Typical signal shape
Single photon irradiation
Catalog spec
Photo-cathode Multi-alkali / Super bi-alkali
MCP Channel φ 10μm
MCP bias angle 13°
MCP thickness 400μm
MCP layers 2
Al protection layer On 2nd MCP
Anode channels 1×4 / 4×4
Sensitive region 64%
HV ~ 3000 – 3500 V
~400m
Channelφ ~ 10μm
~4mmMCP(Micro channel plate)
Performances of SL10
Dec. 1, 2010 6Fast Timing WS, CracowWavelength [nm]
QE
[%]
Multi-alkali PC
TDC [25ps]
Num
ber o
f eve
nts
σtts = 40 [ps]
• All requirements satisfied• Remaining factor: stability(Lifetime)
in high photon rate– ~7x1012 photons/cm2/year– ~0.17 C/cm2/year
• Estimated with TOF trigger hit rate
– Cylindrical type: enough lifetime
ADC [0.25pC]
Num
ber o
f eve
nts
Pedestal
G ~ 106
Single photon irradiation
Dec. 1, 2010 Fast Timing WS, Cracow 7
For single photon test
~40-photon/pulse1k – 40kHz
• Parameters– TTS
• σphotodetector
– Gain• Single photon detection• Enough statistics for TTS
– QE• Ndet
Lifetime measurement for SL10
Load of photons & single photon testdone in same setup
Measured PMT YJ0006 YJ0011
Anode channel 4×4 4×4
Al protection layer 1st MCP 2nd MCP
Initial gain (×106) 0.41 1.1
calibration PMT
Result: TTS, Gain
Dec. 1, 2010 Fast Timing WS, Cracow 8
• Decrease
• Good Stability
– TTS is stable– Single photon
detection is OK
0 0.01 0.02 0.03 0.04 0.05 0.0630405060708090
100 YJ0006 1chYJ0006 6chYJ0011 1chYJ0011 6ch
Output charge [C/cm2]
TTS[
ps]
0 0.01 0.02 0.03 0.04 0.05 0.060.600000000000002
0.700000000000002
0.800000000000002
0.900000000000002
1
1.1YJ0006 1chYJ0006 6chYJ0011 1chYJ0011 6ch
Output charge [C/cm2]
Rela
tive
gain
0 0.4 Time in Belle II experiment [years] No problem
• QE difference– SL10
– Cylindrical
Dec. 1, 2010 Fast Timing WS, Cracow 9
• Lifetime– QE degradation: predominant factor– Gain: linearly decrease; still OK for single photon detection & TTS– TTS: Stability confirmed
Why?
Result: QE
Cylindrical
Previous
SL10
Let’s see QE in detail
QE Variation: Wavelength
• Increase of work function dominatesDec. 1, 2010 Fast Timing WS, Cracow 10
Wave length [nm]
QE
[%]
Before aging
After aging
Work function
Fitting: ratio of QE
Three step model:
T : transmittanceA: mechanical factor (effective region)φ: work function
⊿φ: variation of work function
A(t)/A(t=0) 0.98±0.04 ⊿φ 0.27±0.07eV φ 1.56±0.13eV
YJ0011
QE Variation: Position
Dec. 1, 2010 11Fast Timing WS, Cracow
QE before aging
x [mm]
y [m
m]
QE after aging
y [m
m]
x [mm]
• Surrounding part: large QE drop– Ion feedback?– Structure?
x
y
1
16
Effect of Ion Feedback?• Ion feedback
• Mask: no effect
• Ion feedback
Dec. 1, 2010 Fast Timing WS, Cracow 12
Lifetime test with mask
QE variation without mask QE variation with mask
Positive Iondamages same positionas signal photon irradiation
Lifetime test with mask
Mask
MCP-PMTWindow
Inner Structure & Possible Cause
• Only NEUTRAL gas can pass through gap ( electric field)∵
Dec. 1, 2010 13Fast Timing WS, Cracow
Inner structure of Cylindrical type & square-shaped MCP-PMTs
WindowPC 1st MCP
2nd MCPAnode
WindowPC 1st MCP
2nd MCPAnodeE
Neutral gas
Cylindrical: separated Square: connected
Poisoning of multi-alkali PC with different gasses(INFN Milano – LASA, Via F.lli Cervi 201, 20090)
We also found report saying CO2 and H2O affect QE:(Japanese Journal of Applied Physics 29, No. 10, p. 2087 (1990))
Too much oxidation of Csvariation of band gapincrease of work function
Al-filmCeramic tube
Stainless tube
Al-film
Modification of Inner Structure
• Separate space to PC-side & anode-side– It is not high airtight
• MCPs are changed with that of low outgassing type– To reduce amount of out gas
Dec. 1, 2010 Fast Timing WS, Cracow 14
WindowPC
1st MCP
2nd MCPAnode
CeramicinsulatorCeramic
insulator
Al-film
Lifetime for New SL10
• 2.5 [C/cm2] for relative QE 80%– 1.2×1014[photons/cm2]
Dec. 1, 2010 15Fast Timing WS, Cracow
Aftermodification
Before modification
Rela
tive
QE
Output charge [C/cm2]
0 101 Time in Belle II experiment [year]
DOI:10.1016/j.nima.2010.10.145
SL10 is available
Summary• We are developing TOP counter for Belle-II experiment
– TOF + RICH technique TTS & Nphotons are important
• Square shape MCP-PMT (SL10) is developed for TOP– Satisfies required performances (TTS, gain) for TOP– Lifetime of QE in high photon rate
• We find possible cause of QE drop: Neutral gas (CO2 & H2O)
Improvement of inner structure against gas damage1. Separate space to PC-side & anode-side by ceramic insulator2. Low outgassing MCP
2.5C/cm2 for relative QE 80% achieved– > 10 years under ~7×1012 photons/year/cm2
Dec. 1, 2010 16Fast Timing WS, Cracow
BACKUP
Dec. 1, 2010 Fast Timing WS, Cracow 17
Photon Hit Rate Estimation
Dec. 1, 2010 Fast Timing WS, Cracow 18
Main source: spent electrons EM shower Cherenkov light
TOF hit rate in Belle experiment: 187kHz @ L=1034cm-2s-1
Belle spent electron simulator: 400 – 500 kHz @ L=1034cm-2s-1
Use 500 kHz electron Geant simulationTOP counter is implemented• Quartz radiator: 2650×454×20[mm3]• Without expansion volume• QE: 20% @ λ=400nm• CE: 60%
• To be conservative
Photon hit rate of MCP-PMT: 300kHz/(TOP module)Factor 20 is expected for Belle-II experiment with L~1036cm-2s-1
(20×300 / (45.4×2))×365/2×24×60×60 / (QE×CE)= 6.9×1012 [photons/cm2/year]• effective factor
(20×300 / (45.4×2))×365/2×24×60×60×G×e = 167 [mC/cm2/year]• Gain: 106
☆ Photon hit rate
☆ Typical output charge
Performance of TOP Counter
• Performance definition
• σtop
= √(σMCP-PMT2 + σchromatic
2 + σothers2)
• Ndet: number of detected photons
Dec. 1, 2010 19Fast Timing WS, Cracow
dettop
NTOPTOF
S
Separation power :
Photo-detector is very important
θ z
xy
Ndet 0.8Ndet S 0.9S
Suppression of Chromatic Dispersion
• Wavelength cut
Dec. 1, 2010 20Fast Timing WS, Cracow
Group velocityof light
Number ofCherenkov photons
Transmittance ofwavelength cut filter
350nmSuppression of chromatic dispersionwith 350nm wavelength cut filter
wavelength cut TTS improve⇒
⇒
Ndet decrease fine tune
σchromatic
50 25ps
Path length in quartz: 1m
Number of detected photons
Dec. 1, 2010 Fast Timing WS, Cracow 21
Photo-detector• Requirements
– Gain : 1.0×106
– TTS : <40ps– QE : >20%@λ=400nm– Available in B -field
Dec. 1, 2010 22Fast Timing WS, Cracow
(Micro Channel Plate)
Only photo-detectorsatisfies requirements MCP-PMT
Square type MCP-PMT
Co-developmentwith Hamamatsu Photonics
Channel
~400m
~10m
Channel φ~10μm, Bias angle of MCP : 13° Available in B-field
SL10
Dec. 1, 2010 Fast Timing WS, Cracow 23
Cylindrical & SL10
Dec. 1, 2010 Fast Timing WS, Cracow 24
• Lifetime difference– Cylindrical
– Square
Dec. 1, 2010 Fast Timing WS, Cracow 25
For single photon test
~40-photon/pulse1k – 40kHz
Cylindrical
Square
• Lifetime– QE degradation
• predominant factor– Gain & TTS
• stability confirmed
Why?
Lifetime measurement for SL10
Gain decrease
Dec. 1, 2010 Fast Timing WS, Cracow 26
Before photon load After photon loadOutput charge
• ADC plots
E - λ
Dec. 1, 2010 Fast Timing WS, Cracow 27
How the QE Degradation Occur?
• QE fall is not uniform– Ion feedback is not reasonable
Dec. 1, 2010 28Fast Timing WS, Cracow
x [mm]
QE
[%] (
y =
10[m
m])
QE fallBefore
After
Wave length [nm]
QE
[%]
Before
After
Increase of work function
Before measurement
x [mm]
y [m
m]
After measurement
y [m
m]
x [mm]
How the QE Degradation Occur?
• QE fall is not uniform– It is not reasonable if it caused by Ion feedback
Dec. 1, 2010 29Fast Timing WS, Cracow
x [mm]
y [m
m]
Initial QE
x [mm]y
[mm
]
Terminal QE
x [mm]
QE
[%] (
y =
10[m
m])
QE fallInitial
Terminal
Possibility of neutral gas
Inner structure of CT0790 & square-shaped MCP-PMTs
Neutral gas assumption
Dec. 1, 2010 Fast Timing WS, Cracow 30
Tube
Lifetime of SBA-PC
Dec. 1, 2010 Fast Timing WS, Cracow 31
0 101 Use in Belle II [years]
SBA1SBA2
MA
Set up for Beam Test
Dec. 1, 2010 32Fast Timing WS, Cracow
electron beam( 2GeV/c)
MCP-PMT
TimingCounter
MWPC2
MWPC1
Veto counter
TriggerCounter
TOPCounter
x
y
x
y
Subtract EM-shower events
Beam trajectory
t0 determination
Quartz + MCP-PMTFuji test beam lineat KEK
Prototype test for TOP
• Consistency confirmed
Dec. 1, 2010 Fast Timing WS, Cracow 33
TTS( 1st peak)Data 76.0±2.0 [ps]
Simulation 77.7±2.3 [ps]
ch29
1st
2nd3rd 1st
2nd
3rd
transit time[25ps]
N [p
hoto
ns]
transit time[25ps]
data simulation
Electron beam irradiation
875m
m915m
mquartz
3rd 2nd
1st