Development of HPDs for applications in physics and medical …ndip.in2p3.fr/beaune05/cdrom/Sessions/joram.pdf · 2005. 6. 28. · Beaune 2005 C. Joram CERN / PH Development of HPDs

Beaune 2005 C. Joram CERN / PH Development of HPDs for applications in physics and medical imaging 1

Development of Development of HPDsHPDs

for applications for applications

in physics and medical imagingin physics and medical imaging

A. Braem, E. Chesi, Christian Joram, J. Séguinot, P. WeilhammerCERN / PH

representing the CIMA collaboration and the C2GT team


OutlineOutline

Why Hybrid Photo Detectors ?

Some Developments for physics experiments5-inch 10-inchA spherical HPD for neutrino detection

A flat HPD for 3D-Axial PET scanner

www.cern.ch/ssd/HPD

Great support by our technical staff: F. Cossey, C. David, I. Mcgill, M. v. Stenis, …


Hybrid Photon Detectors (HPD)Hybrid Photon Detectors (HPD)

∆V

photocathode

focusing electrodes

siliconsensor+ FEelectronics

e-

light quantum

segmentedsiliconsensor

Combination of sensitivity of PMT with excellent spatial and energy resolution of silicon sensor

Gain:

Gain is achieved in a single dissipative step !

eV6.3CUeG ⋅

≈ UC = 20 kV → G ~ 5000

small compared to σelectronics

GFG ⋅≈σ


Classical HPD designsClassical HPD designs

• Proximity focused• 1:1 imaging• Operates in axial

magnetic fields.

• ‘Fountain’ focused• Demagnification D• No real focusing→ ballistic point spread

• Intolerant to magnetic fields

• ‘Cross’ focused• Demagnification D• Focusing leads to

small point spread• Intolerant to magnetic

fields


Main advantages of HPD technologyMain advantages of HPD technology• Excellent signal definition• Allows for photon counting• Free choice of segmentation (50 µm - 10 mm)• Uniform sensitivity and gain• no dead zones between pixels

2 p.e.

Drawbacks• Rel. low gain (3000 - 8000) → low noise

electronics required• Expressed sensitivity to magnetic fields

CMS HCAL, 19-pixel HPD (DEP, NL)

Pad HPD

Single padS/N up to 20

1 p.e.

2 p.e.

3 p.e.

Viking VA3 chip (τpeak = 1.3 µs, 300 e- ENC)UC = -26 kV

elec

troni

c no

ise

cut

pulse height (ADC counts)

• e- backscattering from Si surface continuous ‘background’εdet (p.e.) ~ 85-95 %


Some prototype developments for physics experimentsSome prototype developments for physics experimentsdeveloped and built at CERN

NIM A 442 (2000) 128-135

NIM A 478 (2002) 400-403

www.cern.ch/ssd/HPD

5-inch 10-inch

127 mm Ø, D ~ 2.5,2048 channels 1mm2

bialkali photocathode

254 mm Ø, D ~ 4,2048 channels 1mm2

bialkali photocathode

NIM A 504 (2003) 19

NIM A 518 (2004) 574-578


νe, νµ, ντ

CC reactionsin H2O

segmented photosensitive ‘wall’about 250 × 250 m2

Fiducial detectorvolume ~ 1.5 Mt

(Eν below threshold for τ production)

~ 50 m

e±, µ± 42°Che

renko

v ligh

t

Cherenkov light

Principle of neutrino detection by Cherenkov effectin C2GT (CERN To Gulf of Taranto)

The wall is made of ~600 mechanical modules (10 x 10 m2), each carrying 49 optical modules.

10 m

A. Ball et al., C2GT, Memorandum, CERN-SPSC-2004-025, SPSC-M-723

A. Ball et al., Proc. of the RICH2004 conference, subm. to NIM A


The ideal photodetector for C2GTThe ideal photodetector for C2GT

• large size (>10”) • spherical shape, must fit in a pressure sphere• ± 120° angle of acceptance• optimized QE for 300 < λ < 600 nm• single photon sensitive• timing resolution 1-2 ns• no spatial resolution required• electronics included • cost-effective (need ~32.000 !)• adapted to industrial fabrication

120°

42°


432 mm

(17”)380 mm

PAHV

optical gel(refr. index matching + insulation)

benthos sphere(432 / 404)

electrical feed-throughsvalve

standard base plate of HPD 10” (prel. version).

C2GT Optical Module

15

joint Si sensor

ceramic support


ElectrostaticsElectrostatics

Simulations Simulations with SIMION 3Dwith SIMION 3D

110º

-150 -100 -50distance from centre (mm)

-15000

-10000

-5000

0

5000

10000

15000

Φ (V

) or

E (V

/cm

)

Φ ~ 1/r

E ~ 1/r2 • Potential and field distribution similar to

a point charge.

• Low field at photocathode (~100 V/cm),

• Very high field close to Si sensor (~10,000 V/cm). Try to reduce by a grounded field cage around Si sensor.

120º

- 20.3 kV

- 20 kV


0 20 40 60 80 100 1209

10

11

12

Tran

sit t

ime

(ns)

polar angle (deg.)

0 < φ< 120°

Transit TimeTransit Time

9.0 9.5 10.0 10.5 11.0 11.5 12.0Transit Time (ns)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

rel.

frequ

ency

(a.u

.)

σ = 0.15 nsRMS = 0.18 ns

angles > 110°


A A ‘‘halfhalf--scalescale’’ prototypeprototype208 mm (~8-inch)

Al coating2 rings

Development in collaboration with Photonis-DEP, C. Fontaine et al.


Current status: All main components ready ‘dry assembly’

First tests will be done with a metal cube rather than Si sensors


Development for Development for HPDsHPDs for medical imaging for medical imaging The 3D axial PET cameraThe 3D axial PET camera

Axial arrangement of camera modules based on matrices of long crystals read out on both sides by HPDsPreprint CERN PH-EP/2004-050, submitted to NIM A

§ Patent filed. No. WO2004008177 §

HPD2

HPD1

x

y

Principleof a cameramodule

z


Technical realization

208 crystals (YAP)

3.2 × 3.2 ×100 mm3

gap between crystals 0.8

mm

HPD • proximity focused• ceramic body• sapphire window• bialkali PC

2 VATA-GP5 ASIC

Si sensor 2 x 104 pads (4 x 4 mm2)

ceramic PCB (4 layers)


VATA-GP5 (CERN – IDE AS co-development, www.ideas.no)

fast shaper

mask

ORdiscr.

VFP FORTrigger

tresh.

Det.

S/H

slowshaper

AnalogOut

150 ns

25 ns

preamp

• VATA-GP5, 128 ch./chip• Auto-triggering analog front-end• serial and sparse readout• time walk compensation• 0.6 µm CMOS


15 20 25 30 35 40 45 50Vbias (volt)

0

30

60

90

120

sign

al (A

DC

cou

nts)

VATA-GP5 ASIC + ceramic PCB + Si-sensor operational

Si Sensor Depletion(UPC = -15 kV)

5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.50

50

100

150

200

250

sign

al (A

DC

cou

nts)

- UC (kV)0 500 1000 1500 2000 2500

0

50

100

150

200

250

300

350

Qin (fC)

sign

al (A

DC

bin

)sparse readout

serial readoutcut-off at 6 kV(too thick n+ layer)

CaF2

photo-electrons

UV lightsource

CsI

DAQ


2 sealed protoype tubes produced so far… both were not perfect

50 60 70 80 90xmir (mm)

4

6

8

10

12

14

charge vs spot position(centre of gravity)

m = 1.04

centre sensorx d

et (p

ads)

PC109• 50 mm Ø Si-sensor• VA-prime electronics• bialkali cathode (22%)• HV problem

PC113• PET Si-sensor• VATA-GP5

electronics• bialkali cathode• electronics suffered

due to accident during processing

0

4

8

12

16

20

24

Q.E

. (%

)

Photocathode 109 "PCR5" sealedCenter of cathode

250 350 450 550 650

lambda (nm)


Summary and OutlookSummary and Outlook

Our team is developing …

a flat HPD with auto-triggering electronics, aimed at medical imaging applications, in particular PET with single crystal readout.

Sealed fully operational prototype imminent (days!)

a spherical HPD for underwater Cherenkov detector for neutrino physics.

Sealed prototype later this year.

After finally having entered HEP at large scale (CMS, LHCb), HPDs may also have a bright future in some advanced applications(niches?) in other

fields.


BACK-UP slides


0.45 Gauss

B

E~1/r2 produces a focusing effect

effect of earth magentic field seems

to be marginal

Effect of angular spread and magnetic fieldEffect of angular spread and magnetic field• Ekin(t0) = 2 eV (conservative)

• -40º ≤ θem ≤ 40º (rel. to surface)


Is EIs E--field around field around SiSi sensor too high ?sensor too high ?A grounded grid could help

Grid at ‘natural’ potential: -11 kV

-11.000 V

0 V

~23

mm

500 V/mm

1000 V/mm1500 V/mm

2000 V/mm

Gradients up to 2000 V/mm at edges of Sisensor

Grid at 0 V

0 V

0 V

Gradients at Si sensor reduced to ~500 V/mm. High field around grid, f(diam.).

500 V/mm

500 V/mm


Fabrication

Large number of tubes needed industrial fabrication internal process (as for large PMTs).

However, this would lead to a ‘pollution’ of Si-sensor and high field region with Cs/K/Sb.protect by mask (difficult!)use ‘hybrid’ process ?

Q.E. monitoring


Processing in the existing set-up at CERN, used for 5” and 10” HPDs

10”Ø

Only minor mechanical adaptations required.

5”Ø

heating element

glass envelope Sb source

K/Cs sources

base plate with pre-mounted sensor


0 40 80 120 160input charge (fC)

60

70

80

90

100

110

time

wal

k (n

s)

Gain 0Gain 1

+/- 5 ns


vacuum pump (turbo)P < 10-5 mbar

DAQReadout

card

CaF2

Si sensor (300 µm)208 pads (4×4 mm2)

VME

UV H2 flash lamp(self triggering)

CsI photctahode (300 nm)Deposited on a grid(Au, 80% transparency)

MgF2

MgF2

collimator

mirror

mask (at ground)photo-electrons

Experimental set-up for VATA-GP5 tests with photo-electrons

-UPC = 15-20 kV

Documents

Development of HPDs for applications in physics and medical …ndip.in2p3.fr/beaune05/cdrom/Sessions/joram.pdf · 2005. 6. 28. · Beaune 2005 C. Joram CERN / PH Development of HPDs