Transcript Hybrid Photo Pixel Detector

Ashra Report:
Hybrid Photo Pixel Detector as
the Trigger Sensor
Masataka Masuda
(Tokyo Institute of Technology)
for Ashra collaboration
31 Oct 2006, DPF2006
Ashra Collaborators
Y. Aitaa, T. Aokia, Y. Asaokaa, T. Browderi,
T. Chonana, S. Dyei, M. Eguchia, R. Foxh,
S. Fukagawab, G. Guilliani, J. Hamiltonh,
M. Ieirie, T. Kimurac, N.Kohtaf, I. Kogab, H. Kuzeb,
J. Learnedi, N. Managoa, M. Masudag, S. Matsunoi,
Y. Morimotof, K. Nodaa, S. Ogawaf, A. Okumuraa,
S. Olseni, M. Sasakia, H. Shibuyaf, N. Sugiyamad,
M. Yasudag, G. Varneri , Y. Watanabeg, Y. Watanabef
(a) ICRR, Univ. Tokyo (b) Chiba Univ. (c) Ibaraki Univ.
(d) Nagoya Univ. (e) KEK (f) Toho Univ. (g) Tokyo Inst. Tech.
(h) Univ. Hawaii Hilo (i) Univ. Hawaii Manoa
Contents
1. Introduction
2. Image Pipeline of Ashra detector
3. Hybrid Photo Pixel Detector
4. CMOS Fine Sensor
5. Summary
Introduction: Ashra Detector
Distinctive Features:
• 12 detectors/station All-sky Survey
2πsr80%
• FOV / detector 0.42sr
• High resolution a few arcmin
•Hybrid detection
U.V., Cherenkov and fluorescence
lights
Self-trigger system for hybrid detection
• Signal delay with slow decaying phosphor screen
• Pattern recognition in Trigger sensor
• Fine sensor with local exposure and readout
Pilot Observation of Cherenkov Showers
Proton Shower Candidate
Exposure: 200ns
Each spot corresponds to individual incoming photon.
Succeeded in self-triggering with almost final setup
For wide FOV, technical developments are required for trigger.
Image Pipeline of Ashra detector
Distributes same image to 4 sensors keeping good resolution and
brightness with I.I.s, splitters and optical fibers.
Untriggerd image sensor
20inch UV I.I.
Amp I.I.
Half mirror
1
Delay
Delay I.I.
I.I.
Fine Sensor
4
Optical Fiber
Photon
electron
Trigger Sensor
2
Cerenkov
3
fluorescence
Requirements for trigger sensors
•trigger judgement within ~200ns
•high resolution to recognize AS image
=>Hybrid Photo Pixel Detector
Afterglow sustains
~200ns
200ns
Hybrid Photo Pixel Detector
Electron tube, silicon pixel detector and readout LSI circuits

Prototype
LSI chip
Focusing Electrodes
e
-
Photocathode
VACUUM
6inch
Silicon detector
307mm
Main features
•De-magnification by ~ 5
•6464 pixel silicon anode (450m450m each)
•Trigger LSI chip for fast pattern recognition
•Bump bonding and vacuum feedthroughs
High resolution and Fast response are required
Radial height (mm)
Simulation of electron trajectories
Electron Trajectories
electrodes
Distance from the input surface (mm)
Electron trajectory simulation
 Optimize shape of input window, positions of electrodes
and high voltages applied to them
We simulated Point spread of photoelectons on the silicon detector
Simulated Point spread on silicon detector
Point spread as a function of input radius
Definition:Meridonal and sagittal
direction
Meridional
direction
Meridional
0.45mm line (pixel
size)
Input radius
Sagittal direction
Input window
Sagittal
Full width including 84% of photoelectrons
0.45mm line (pixel
size)
<< Pixel size of silicon detector (0.45mm)
at any input radius
Electron tube with high resolution is
designed.
Silicon Pixel Detector
Rear
Technical features
n+
•Simple p+ n type
250µm
h+ eh+ eh+ e-
•Depletion voltage 65-105V
n-sub
sectional view
p+
e-
•6464 pixel array
450µm
Front
(Number of pixels is maybe largest! )
20µm
• Bump bonded to LSI readout chips
6464
28840µm
surface
30800m
28840µm
430m
30800m
•Electron collection for fast response
PAD
Crosstalk, Response and Dark currents are
simulated.
Electric fields and Currents in Silicon Detector
Local electric field concentration => Currents increase with avalanche
Designed carefully to prevent avalanche breakdown.
Dark current of 0.3nA/pix.
<< Signal current ~ a few A (1TeV Gamma ray)
Crosstalk and Response in Silicon detector
Electrode
Simulation
・Electric fields in 33 pixels
・ Electrons trajectories
・Drift time of electrons
Trajectory
h+
-100V
e－
e－
Results
・Crosstalk ~ 0
trajectory // z direction
・Fast responce
drift time ~ 6ns
Silicon detector with low crosstalk is well designed.
Trigger LSI circuits
16x16 discriminator array equipped on the back of HPD
Circuit Diagram of a pixel
9.8mm
9.8mm
Characteristics
•Each pixel consists of I-to-V converter, filter and comparator.
•Time constant can be changed.
•Threshold voltage can be changed with control signal.
Response in Trigger LSI was measured.
Timing Test of Trigger LSI
Circuit board for Trigger LSI
Input: 200ns Pulse
Pulse Gen.
DCV
Output
LSI
Scope
threshold
Output
50ns
LSI chip with BGA
Input
9.8mm
Typical delay time in each pixel = 50ns
< Delay I.I. afterglow sustains for ~ 200ns
Exposure and Readout Control of CMOS Sensor
1. Signal hits pixels in trigger LSI
2. Output X and Y Wired- OR
trigger pulses
3. Address the region in
Fine sensor
4. Start exposure and hold Q
5. Repeat 1~4 with
overlapping
6. Finally take AS
image with any
duration and at any
time
CMOS fine sensor
Standard CMOS process
2-poly 3-metal 0.35µm
• Chip size
1919mm
• Number of Cells
128128
• Pixels in the Cell 1616
• Number of pixels 20482048
• Pixel size
88µm
• Readout
12.8s/Cell
Trigger rate (Proton Cherenkov BG) ~ 1kHz
 Exposure and readout for each cell
Imaging with CMOS Fine Sensor
F-Mount
Control
Signals
CMOS
Sensor
Ashra
CMOS
Sensor
A/D Converter
Processor
Board
An Image was focused onto the CMOS
sensor
Processor board generates trigger signal
and selects readout cells.
Succeeded in obtaining image with
100ns exporsure
Personal
Computer
Y-Trigger
X-Trigger
Summary and future plans
Hybrid Photo Pixel Detector
/ Electron tube and silicon detector are well designed.
High resolution, fast response and low crosstalk are simulated.
/ Readout LSI circuit has been developed.
Response time of 50 ns was measured.
CMOS fine sensor has beed developed
Image with 100 ns exposure is obtained.
Silicon pixel detector is scheduled for completion in next December.
Self-trigger with HPD and CMOS sensor will be coming soon.