development of 144ch hapd for aerogel rich for belle...

Jun. 17, 2008Development of 144ch HAPD

for Aerogel RICH for Belle UpgradeNDIP2008

1S.Nishida (KEK)

S. Nishida

Development of 144ch HAPDfor Aerogel RICH for Belle Upgrade

NDIP2008Jun. 17, 2007

KEK



2S.Nishida (KEK)

Contents●Introduction.●144ch HAPD ●HAPD Readout with ASIC●Beam Test●Summary

I. Adachia, R. Dolenecb, K. Harac, T. Iijimac, H. Ikedad,Y. Ishiie, H. Kawaie, S. Korparb,f, Y. Kozakaic, P. Križanb,g,

E. Kurodai, Y. Miyazawah, S. Nishidaa, I. Nishizawai,S. Ogawaj, R. Pestotnikb, N.Sawafujij, S. Shiizukac,

T. Sumiyoshih, M. Tabatae, Y.Uekih

aKEK, bJožef Stefan Institute, cNagoya Univ., dJAXA,eChiba Univ., fUniv. of Maribor, gUniv. of Ljubljana,

hTokyo Univ. of Science, iTokyo Metropolitan Univ., jToho Univ.



3S.Nishida (KEK)

Introduction

upgrade

aerogelradiator

photodetector

● PID has been a key issue in B factory experiments. The situation is the same in future B factory:

• bd v.s. bs, flavour tagging ...● ACC (Aerogel Cherenkov Counter) is used in Belle.

● Threshold type● Separation only up to ~ 2GeV in the endcap region

● As an upgrade of the endcap ACC, we are developing Proximity Focusing Aerogel RICH. Aerogel RICH

ACC



4S.Nishida (KEK)

Introductionphotodetectoraerogel

radiator

200mm

● Target: 4 /K separation at 1<p<4 GeV/c.● () (K) = 23 mrad for 4 GeV/c particle

(in case of aerogel radiator with n=1.05). ● Limited by the space.

The scheme of Aerogel RICH has been confirmed by a test using 4×4 array of flatpanel PMT (Hamamatsu H8500)

52.5m

m

However, H8500 cannot be used in the magnetic field.



5S.Nishida (KEK)

144ch HAPD

● Position sensitive (~ 55 mm2); Large effective area.● Immune to 1.5T magnetic field. ● Coverage of Belle endcap region (~ 22 m2; 105 channels)

Requirement to photodetector

Candidate: 144ch HAPD (Hybrid Avalanche Photo Detector)photon

bombardmentgain ~ O(1000)

Pixel APD avalanche gain ~ O(10)Total gain ~ 104105

8kVHV

300Vbias

multialkaliphotocathode

● Developed with Hamamatsu Photonics.● 144 channels, 4 APD chips (36ch/chip)● Effective area 64mm64mm (65%).



6S.Nishida (KEK)

HAPD Performance

pedestal

1 p.e.

Pulse Height

Pulse Height DistributionNoise level

● Bias voltage dependence of Noise.● Measured with HV OFF.● Noise level is estimated from the width

of pedestal. ● Full depletion at >50V.● Leakage current increases at ~300V.● No large chip dependence.

Clear separation between pedestal and 1 p.e. peak!!

● Measured with HV ON.● Light source: LED.



7S.Nishida (KEK)

HAPD Performance(×100)

● Gain of 4 HAPD samples for each APD chip.● Measured with HV –7kV.● Typical gain 40000100000. ● Avalanche gain depends on chip and bias voltage.



8S.Nishida (KEK)

Readout with ASICReadout system requires:

□4.93[mm]

● High density frontend electronics (100k ch)● High gain with very low noise amplifiers● Deadtimeless readout scheme (Pipeline)

We have developed ASICs for the frontend electronics.analog digital

Preamp Shaper VGA Comparator Shift Register

● Production at VDEC (Tokyo Univ)● Process: ROHM CMOS 0.35 [m]● Target Noise Level: 1200 [e] @ 80pF (HAPD)● Std. Input Signal: 12000 e● #(channel) = 18 [ch/chip]● Power Consumption = 3 [mW/ch]

● Shaping time 0.3 ~ 2.0 [s]● Variable gain 1.25 ~ 20● Common threshold.● Channelbychannel offset

adjustment (±200 mV)



9S.Nishida (KEK)

HAPD Readout with ASIC

LED

HAPD ASIC LED off LED on

Successfully readout 1 p.e. levelsignal from HAPD using ASICfor the first time!!

● Distribution of output of ASIC (digital) for 1000 LED clocks.

● Irradiate 1p.e. level photon to 1 channel.

LED off LED on

varying ASIC threshold 1 p.e.

2 (or more) p.e



10S.Nishida (KEK)

HAPD Readout with ASIC

LEDon stage

HAPDboard

w/ ASIC

● 2d scan with 0.4mm step.● LED on xy stage.● Several dead channels from

HAPD and ASIC. (0~3 per APD chip and 0~2 per ASIC)

8 ASIC for 1 HAPDEdge channels sometimes haveinefficiency/crosstalk (distortion of electric field inside tubes)

(might be recovered in the magnetic field)



11S.Nishida (KEK)

Beam Test at Fuji Beam Line

~2 GeV electron beam converted from Bremsstrahlung photons from KEKB main ring (electron) at Fuji area (opposite site of Belle detector).

8 GeV electron

We performed two beam tests for Aerogel RICH

Mar 17th23rdJune 5th12th

3 km

FujiLinac

BelleKEKB

Bremsstrahlung photon e

e



12S.Nishida (KEK)

Beam Test Setup● Tracking using 2 MWPC● 2 × 3 array of 144 ch HAPD● HV at –7kV. ● Bias voltage of HAPD is chosen

at avalanche gain = 40.(or maximum bias voltage).

● Readout using 48 ASICs.● ASIC offset is adjusted so that

the noise is below the threshold. threshold is typically ~ 0.5 p.e. level, but depends on each channel's gain and noise level.

● Standard aerogel (n = 1.045, thickness = 20mm, transmission length = 41mm @400nm), and many other aerogels.



13S.Nishida (KEK)

Cherenkov Ring ObservedSucceeded to observe Cherenkov Ring using HAPD!!



14S.Nishida (KEK)

Cherenkov Ring Observed

N(p.e.) = 4.8c = 12.4 mrad

● Clear Cherenkov ring is observed!● 4.8 photoelectrons per track.

● Consistent with the old result with Flatpanel PMT (6.4 p.e.) if we consider smaller acceptance (84% 68%) and gap btw HAPD.

● Resolution 12.4 mrad per photon (was 13.6 mrad)● Single track resolution 5.7 mrad corresponding to 4.0 K/ separtation.

Result of quick analysis for a run with 2cm aerogel radiator preliminary



15S.Nishida (KEK)

BackgroundOld result

with flatpanel PMTHowever, background shape is different

halo?

beam induced hits,but why two peaks?

additional structure

Beam tends to pass the upper HAPD; the additonal structure is considered to be related to the beam.



16S.Nishida (KEK)

BackgroundPossible explanation

Cherenkov RingReflection @ AD

Cherenkov @ glass + reflection @ ADCherenkov @ glass + reflectionCherenkov @ glass / direct hit to AD

Back scattering electron

● AD is visible● 4mm thick glass

(1.5mm for Flatpanel PMT)

In order to understand the source of the background, we have tested different configuration (thicker glass, incident angle dependence) .

might not be aproblem in themagnetic field



17S.Nishida (KEK)

Threshold DependenceThreshold dependence

190mV 290mV390mV

490mV 590mV 690mV

nominal setting

● Reasonable behaviour.● Background inside the ring also disappear

except the background in the center.● Fine scan is done in the second beam test.



18S.Nishida (KEK)

Focusing RICH● Thicker aerogel increases N(p.e.), but makes

resolution worse.● One solution is “focusing” RICH.● Superimpose rings from two (or more)

radiators with different indices. n1 n2(n1<n2)

Np.e

resolutionsingle trackresolution

aerogel indecies 1.046, 1.050, 1.056, 1.064 for multiple radiator.

This focusing scheme was already studied before;confirmed by the beam test with HAPD



19S.Nishida (KEK)

Summary● As an upgrade of the endcap ACC in Belle, we are developing Aerogel RICH

detector.● 144 ch HAPD is a perspective candidate of the photodetector.

Single photon peak can be clearly observed.● Readout using ASIC

Successfully readout 1 p.e. level HAPD signal using ASIC.● Beam test with a 2 × 3 array of 144 ch HAPD.

Cherenkov ring is observed with HAPD for the first time! Reasonable performance (Np.e.; resolution) Unknown background inside the ring (reflection at AD ...).

Future Plan● More configuration has been studied in the second beam test; data will be

analyzed soon. Understand background; more realistic HAPD configuration etc.

● New version of ASIC was delivered. To be tested.● Test under 1.5T magnetic field.



20S.Nishida (KEK)

Backup



21S.Nishida (KEK)

Aerogel RICH Development

2000

cherenkov ring byimage intensifier

2001

6×6 multianode PMT(R5900M16)

2002

4×4 flatpanel PMT(H8500)

(angle) = 14mradN(p.e.) = 6

20032005 2004

Focusing Type

Try to increasedetected photonswithout makingthe resolution

worse(angle) = 13mradN(p.e.) = 9

basic principle systematic study

performance improvement

2006

HAPD etc.



22S.Nishida (KEK)

144ch HAPDHistory

2002 single channel HPD2003 33channel HAPD2004 1st prototype of 144channel HAPD

2007 Aug new (good) sample

..... many dead chips, large noise

● All the 4 chips are alive.● Quantum efficiency ~ 26.9% (peak)● Maximum high voltage to photocathode = 8.5kV● Maximum bias voltage:

chip A: 331V, chip B: 331V,chip C: 337V, chip D: 343V

earlier sample

noise

measure the performance



23S.Nishida (KEK)

Experimental Setup



24S.Nishida (KEK)

UniformityMeasure uniformity for one APD chip (36 ch)

Gain

S/N

Gai

n

S/N

too noisy with bias voltagedominated by the crosstalk from neighboring channel

● No large channel dependence in gain, S/N.● Problem in the channels at edge.

Similar effects seen in old samples. Maybe distortion of the electric field

inside the tube?



25S.Nishida (KEK)

ASIC SpecificationSpecification:

● Production at VDEC (Tokyo Univ)● Process: ROHM CMOS 0.35 [m]● Target Noise Level: 1200 [e] @ 80pF (HAPD)● Std. Input Signal: 12000 e● #(channel) = 18 [ch/chip]● Readout: Pipeline with shift register● S/N = 10● Power Consumption = 3 [mW/ch]

measured noise level

~1900 e @ 80 pF

● Shaping time 0.3 ~ 2.0 [s]● Variable gain 1.25 ~ 20● Offset adjustment

Overall 200 mV Channel by channel 30 mV Capacitance [pF]

Noi

se [e

]

80pF (HAPD)



26S.Nishida (KEK)

ASIC PerformanceOffset adjustment

ASIC Channel ASIC Channel

offset offset

test pulse peak test pulse peak

100mV 30mV

Puls

e he

ight

[mV]

Puls

e he

ight

[mV]

before after

Gai

nD

iffer

ence

Linearity

1 p.e.

2 p.e.

3 p.e. Gain= 5

Gain=2.5

(In this plot,1 p.e. is assumed to be 12000e).

Linearity with reasonable range.

Puls

e he

ight

[mV]



27S.Nishida (KEK)

HAPD Readout with ASICHAPD ASIC (8 chips)

digital I/O board(VME)

Readout of HAPD signal with the ASIC is tested.

● The surface of HAPD is covered by a black sheet except for one channel.

● Light corresponding to ~10 photons is emitted from LED.

● Trigger for readout is provided from LED control signal.

● Threshold is set to ~30000 e.LED

HAPD ASIC

monitor signal of ASIC

Only 2 ASICs are connected.



28S.Nishida (KEK)

HAPD Readout with ASICLED OFF

LED ON

● Distribution of output of ASIC (digital) for 1000 LED clocks.

● All the channels except the center are covered by black sheet.

Successfully readout all the channels in one (APD) chipsusing 2 ASICs, simultaneously

A big step for HAPD readout



29S.Nishida (KEK)

ASICIn parallel, we start developing a new version of ASIC● Present ASIC (developed for evaluation) is not enough for readout of large

amount of channels.● Drop out the digital part (shift registers) from the ASIC, so that it becomes

more flexible. Digital part will be provided by external FPGA.● More channels per chip (18 36 or 72).

New ASIC will be submitted on December● Test production at MOSIS.● TSMC 0.35 m processes . ● With 12ch (with 3 3mm2 chip) this time,

but with more channels (e.g. 3 8mm2 chip) in future. An

alog

inpu

t

Dig

ital o

utpu

t



30S.Nishida (KEK)

HAPD PerformanceMultiphoton Bombardment gain (by Hamamatsu)

Q.E.



31S.Nishida (KEK)

Uniformity

Position Resolution

0.1mm pitchscan

ch1

ch2 ch3 ch4 ch5 ch6

photon incident position

Problem in ch1(channel at the edge)

insideoutside

<Measurement for the old sample>

photon

electron

photo cathode

Distortion of electric field ?

● If so, the situation becomes better with the (1.5T) magnetic field.

● Will be tested.



32S.Nishida (KEK)

Threshold ScanMeasure the efficiency of digital output varying the threshold.

Estimate the pulse height and noise.

pulse height noise

(1)

(2)(3)



33S.Nishida (KEK)

ASIC Analog Part



34S.Nishida (KEK)

ASIC Digital Part

development of 144ch hapd for aerogel rich for belle...

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