high resolution imaging with mcp detectors using delay line anodes
DESCRIPTION
High resolution imaging with MCP detectors using delay line anodes. Ottmar Jagutzki, Uwe Spillmann, Achim Czasch. Horst Schmidt-Böcking, Reinhard Dörner, …. In collaboration with Volker Dangendorf fromPTB Braunschweig, Neutron Radiography group. The helical wire delay-line anode. - PowerPoint PPT PresentationTRANSCRIPT
High resolution imaging with MCP detectors using delay line anodes
Ottmar Jagutzki, Uwe Spillmann, Achim Czasch
Horst Schmidt-Böcking, Reinhard Dörner, …
In collaboration with
Volker Dangendorf from PTB Braunschweig, Neutron Radiography group
The helical wire delay-line anode
Fast timing electronics high rate, multi-hit 5(7) electronic channels only easy read-outCenter-of-mass averaging high position resolution
time resolution: < 1 ns
Sobottka and Williams 1988
DLD40
80 mm “Hexanode” delay-line detector (patented)
Our typical resolution: 40-50 μm rms
Electronic readout:
Time-to-Digital-Converter:
- (old) Wilkinson-type analog-digital conversion (like a TAC): high resolution but a slow digital conversion
- “counter”-type fast (no!) conversion: resolution limited by clock rate Pretty high resolution and fast read-out
TDC8HP: PC-controlled multi-hit TDC with 8 channels, 25 psec LSB, stableread-out speed: 400 kHz now, up to 2 MHz planned (< 10 ns dead-time between hits)
“TDCHP” chip developed by CERN
How to detect visible/near-UV photons with that ?
Photek 75 mm image intensifier with RoentDek DL80 anode
NASA test mask
0.15 mm FWHM
0.075 mm pixel (rms)
Now: < 40 micron rms
5 mm grid constant, 1 mm obstacle
Counting/Imaging near-UV and visible photons with delay-line read-out
DL40-PMT
Quartz windowPhoto cathode
MCP stack
DL40 anode(or bigger)
works fine, but
- difficult to build- not very robust (?)
- size up to 150 mm possible?
Counting/Imaging near-UV and visible photons with delay-line read-out
via image charge pick-up: the RS-PMT
Quartz windowPhoto cathode
MCP stack
Resistive screen
pickup electrode(e.g. delay-line)
Patented technique
- easy, robust design of detector head- size up to 40 mm, may be bigger- standard (multi-layer) PCB pickup electrodes
Image charge read-out: Battistoni et al. 1982
Counting/Imaging near-UV and visible photons with reconfigurable read-out
Quartz windowPhoto cathode
MCP stack
Resistive screen
otherpickup electrodes:
Wedge&Strip, Pixel,…
Patented technique
Read-out technique can easily be reconfigured using the same detector head.
Counting/Imaging VUV photons or particles with reconfigurable read-out
“open RS-PMT”
MCP stack
Resistive screen
pickup electrodes:
Delay-line, Wedge&Strip, Pixel,…
Patented technique
Image charge read-out has some advantages over charge collection for some anodes: Beneficial even for open-face detectors
Delay-line read-out of RS-PMT:
Multilayer PCB
Front and rear side “antennas” (Eland 1994)
connected to delay-line:
(Berkeley group) LC-delay-line
LC-DL50 on open RS-PMT40, irradiated with α – particles, mesh obstacle 80 micron
LC-DL50 on open RS-PMT40, irradiated by ions with 500 kHz, mesh obstacle 80 micron
LC-DL50 on open RS-PMT40, irradiated by ions with 500 kHz, mesh obstacle 80 micron
8 x 8 mm linear scale log scale
50 mm LC Hex-DL on a 4-layer PCB
Hexanode for RS-PMT:
- multi-hit (simultaneous photon pair detection is possible): Compton telescope?- intrinsic linearity correction (no test mask necessary): 3 combination for determining x- and y-coordinates from u, v, w coordinate system
Example for x-layer: x = u = - (v + w) (over-determination) (vector addition)
u
v w
x = u
y =
(w
- v
)/√3
But how can this help correcting non-linearity ?
Linearity correction of LC-delay-line: (no mask needed)
of RS-PMT: 16 18 20 220
20
40
60
80
100
120
140
rela
tive
char
ge /
%
position / mm
Experiment 4 (d=1.0 mm)
Gauss Fit X
c=18.9 mm
=0.86 mm
2,0 mm
Summary:
- Large (open-face) MCP delay-line detector with up to 3000x3000 pixel
- Resistive screen PMT or open MCP detector for counting photons (might qualify for space)
- redundant triple-layer delay-line anode read-out with intrinsic linearity correction
- read-out anodes can easily by swapped
work to be done:
- position resolution needs to be improved for the 40 mm and 25 mm formats
- no experience with flight mission
- not much experience with photon counting at all !
Applications:- FLIM (fluorescence life-time microscopy) - NEURRAD (element sensitive neutron radiography) in cooperation with Volker Dangendorf, PTB Braunschweig
Thanks to Jürgen Barnstedt from Tübingen for borrowing us his RS-PMT!
Obj
ect
Projection of grid mask 70/600micron, resolution 35 micron (1:700)
Results of Barnstedt et al. (1998)
25mm RS-PMT (Proxitronic) - bi-alkali photo-cathode - 4-jaw Wedge&Strip anode