2007/10/15-20 6th International Workshop on Ring Imaging Cherenkov Counters
Development of TOP counterfor Super B factory
- Introduction- Design study
- PMT property- Focusing system
- Summary
K. Inami (Nagoya university)
2007/10/15-20 RICH07 2
Introduction
Side view of Super Belle detector
2.6m
1.2m
e-
8.0GeVe+
3.5GeV
1.5T
TOP (Time Of Propagation) counterDeveloping to upgrade the barrel PID detectorFor Super B factory
Lpeak~1035~36/cm2/s, 20~100 times higher than presentNeed to work with high beam BG
To improve K/π separation powerPhysics analysis
B ππ/Kπ, ργ, Kνν etc.Flavor tagFull reconstruction
Target; 4σ for 4 GeV/c
2007/10/15-20 RICH07 3
TOP counterCherenkov ring in quartz bar
Reconstruct ring image using ~20 photons on the screen reflected inside the quartz radiator as a DIRC.
Photons are detected with photon detectors.
πK
x
y
θc = cos (1/nβ)
Quartz : n = 1.471 (@λ=390nm)
Φ
Different ring image for the pion and kaon of the same momentum
Need large screen...
2007/10/15-20 RICH07 4
TOP counter2D position information Position+Time
Compact detector!~400mm
Linear-array type photon detector
LX
20mm
Quartz radiatorx
y
zLinear array PMT (~5mm)Time resolution σ~40ps
~2m
12000
14000
16000
18000
20000
22000
24000
26000
28000
30000
-20 -10 0 10 20
TD
C (
ps)
X (cm)
Kπ
Simulation2GeV/c, θ=90 deg.
~200ps
Different opening angle for the same momentumDifferent propagation length(= propagation time)
+ TOF from IP works additively.
2007/10/15-20 RICH07 5
Test counter
0
50
100
150
200
250
300
-100 -50 0 50 100x (mm)
TOP
(
ch/2
5ps)
2 3 4 5TDC (ns)
6 gaussian fit.
σcommon = 82.ps
TDC distribution (x=11.3mm)
Quartz bar spec. Quartz : sprasil P20 (Synthetic fuzed silica,
made by shin-etsu co.) size : 1000mm 200mm 20mm surface : 0.5nm(rms), figure < 2µm squrness : < 0.3mrad, edge radius < 5µm polished by Okamoto optics work,inc
1000mm
PMT HPK R5900-U-L16
200mm
Test counterBeam test@ KEK PS π2 line
3 GeV/c π− beamθin=φin=90 degree
• Clear ring image
• Reasonable time resolution
• Enough bar quality
1mm pitch readout
2007/10/15-20 RICH07 6
DesignQuartz: 255cmL x 40cmW x 2cmT
Cut at 47.8deg. to reduce chromatic dispersion
Multi-anode MCP-PMTGood time resolution (<~40ps), Linear array (5mm pitch)Three readout planes
IP
Forward BackwardPMT
32.8o~123.5o
47.8o 1180mm
z=1830mm z=1070mm z=-780mm
5mm
40cm
2cm
MCP-PMT
2007/10/15-20 RICH07 7
ChromaticityDetection time depending on the wavelength of Cherenkov photons
Worse time resolution→ Worse ring-image separation
Propagation velocity depending on λ in the quartz bar
12000
14000
16000
18000
20000
22000
24000
26000
28000
30000
-20 -10 0 10 20
TD
C (
ps)
X (cm)
300
400
500
600
16000 20000 24000 28000
TDC(ps)0
100
200
16000 20000 24000 28000
λ(nm
)
π, 2GeV/c, θ=90deg., ch=40
2007/10/15-20 RICH07 8
Chromatic dispersionVariation of propagation velocity depending on the wavelength of Cherenkov photons
0
5
10
15
20
25
30
35
40 Bi-alkali
GaAsP
photon lambda(nm)
QE
(%)
300 400 500 600 700
Multi-alkali
GaAsP photo-cathode ( alkali p.c.)Higher quantum-efficiency at longer wavelength → less chromatic error
0.19
0.2
0.21
300 400 500 600 700Wave length (nm)
Gro
up v
eloc
ity (m
/ns) Light propagation
velocity inside quartz
Photon sensitivity at longer wavelength shows the smaller velocity fluctuation.
2007/10/15-20 RICH07 9
GaAsP MCP-PMT developmentSquare-shape MCP-PMT with GaAsP photo-cathode is developed with Hamamatsu Photonics.
PrototypeGaAsP photo-cathode
Al protection layer
2 MCP layersφ10µm hole
4ch anodesSlightly large structure
Less effective area
Performance testTime resolution
22(effective area)27.5mm
1ch
2ch
3ch
4ch
Target structure
DISC
PLP PMT ATTN AMP DIV
TDC
ADCFILTER
BLACK BOXDISC
λ=407nmJitter~10ps
there 100mV
36dB
there 20mV
25ps/1bin
CAMAC
START
GATE
DISC
PLP PMT ATTN AMP DIV
TDC
ADCFILTER
BLACK BOXDISC
λ=407nmJitter~10ps
there 100mV
36dB
there 20mV
25ps/1bin
CAMAC
DISC
PLP PMT ATTN AMP DIV
TDC
ADCFILTER
BLACK BOXDISC
λ=407nmJitter~10ps
there 100mV
36dB
there 20mV
25ps/1bin
CAMAC
DISC
PLP PMT ATTN AMP DIV
TDC
ADCFILTER
BLACK BOXDISC
λ=407nmJitter~10ps
there 100mV
36dB
there 20mV
25ps/1bin
CAMAC
PLP PMT ATTN AMP DIV
TDC
ADCFILTER
BLACK BOXDISC
λ=407nmJitter~10ps
there 100mV
36dB
there 20mV
25ps/1bin
CAMAC
START
GATE
2007/10/15-20 RICH07 10
GaAsP MCP-PMT performanceWave form, ADC and TDC distributions for single photon
Enough gain to detect single photo-electronGood time resolution (TTS=35ps) for single p.e.
Single p.e.0.5ns/div20mV/div
ADC
0
100
200
300
400
500
600
100 120 140 160 180/0.25pc
cou
nt
pedestal
single photon peak
Gain~0.64×106
Time
0
1000
2000
3000
-20 -10 20/25ps
cou
nt
0 10
TTS~35ps
2007/10/15-20 RICH07 11
IP
Forward BackwardPMT
32.8o~123.5o
47.8o 1180mm
z=1830mm z=1070mm z=-780mm
0
2
4
6
8
10
12
14
16
40 60 80 100 120polar angle (deg.)
Sep
arat
ion
pow
er (
σ)
2GeV/c3GeV/c4GeV/c
90
92
94
96
98
100
40 50 60 70 80 90θ (deg.)
Effi
cien
cy (
%) 2.0GeV/c
3.0GeV/c
4.0GeV/c
0
2
4
6
8
10
40 50 60 70 80 90θ (deg.)
Fak
e ra
te (
%)
2.0GeV/c3.0GeV/c
4.0GeV/c
K/π separation powerGaAsP photo-cathode + >400µm filter, CE=36%
3.5σ K/π for 4 GeV/c, θ=70゚
Performance with GaAsP
2007/10/15-20 RICH07 12
Focusing TOP
Focus Mirror
y
PM
T
Side view
Mirror image
Remaining chromatic effect makes ~100ps fluctuation for TOP.Use λ dependence of Cherenkov angle to correct chromaticityFocusing system to measure θc
λ θc y positionReconstruct ring image from 3D information (time, x and y).
))(1
(cos=)( 1
βλnλθ c
ー
Rotate PMT
Focus Mirror
2007/10/15-20 RICH07 13
Focusing TOP (2)∆θc~1.2mrad over sensitive λ range
∆y~20mm (~quartz thickness)We can measure λ dependence and obtaingood separation even with narrow mirror and readout plane, because of long propagation length.
Not need focusing blockNot need fine readout channels
1850mm
Virtual readout screen22mm x 5mm matrixFocusing
mirror
∆θc~1.2mrad
2007/10/15-20 RICH07 14
Performance of focusing TOPK/π separation power
GaAsP photo-cathode(+>400µm filter), CE=36%
40 50 60 70 80 90polar angle (deg.)
0
1
2
3
4
5
6
Sep
arat
ion
pow
er (
σ)
95
96
97
98
99
100
40 50 60 70 80 90
0
1
2
3
4
5
40 50 60 70 80 90polar angle (deg.)
Effi
cien
cy(%
)F
ake
Rat
e(%
)4
Separation power Efficiency,Fake rate@ 4GeV/c
4.3σ separation for 4GeV/c
2007/10/15-20 RICH07 15
Mirror test
Focusing mirror
2cm
40cm
Spherical mirror (R=5m)
Prototype by Okamoto-optics40x2x2cm, R=5mAttached at the end of quartz bar
Shape measurementNeed continuous mirror image
Found (4.9±0.2)mm shiftAdjusted by re-polishing flat planes
Focus Mirror
y
PM
T
Laser depth meter
2007/10/15-20 RICH07 16
SummaryR&D of TOP counter is in progress!
To install super B factoryDesign studies
To suppress the influence of chromaticityGaAsP photo-cathode MCP-PMT
Prototype shows the enough performanceGain = 0.64x106, TTS = 35ps for single photonHigh Q.E. (>40% at 500nm)
Focusing systemNarrow mirror and narrow readout planeForm large virtual readout screen
Not need focusing block and fine PMT channelsImproved performance (4.3σ for 4GeV/c)
Prototype production