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
DLD40
Sobottka and Williams 1988
Fast timing electronics

high rate, multi-hit
5(7) electronic channels only 
easy read-out
Center-of-mass averaging

high position resolution
time resolution: < 1 ns
Our typical resolution: 40-50 μm rms
80 mm “Hexanode” delay-line detector (patented)
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:
 Pretty high resolution and fast read-out
resolution limited by clock rate
TDC8HP:
PC-controlled multi-hit TDC with 8 channels, 25 psec LSB, stable
read-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
5 mm grid constant, 1 mm obstacle
0.075 mm pixel (rms)
Now: < 40 micron rms
Counting/Imaging near-UV and visible photons with delay-line read-out
DL40-PMT
Quartz window
Photo 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 window
Photo cathode
MCP stack
Resistive screen
pickup electrode
(e.g. delay-line)
- easy, robust design of detector head
- size up to 40 mm, may be bigger
- standard (multi-layer) PCB pickup
electrodes
Patented technique
Image charge read-out:
Battistoni et al. 1982
Counting/Imaging near-UV and visible photons with reconfigurable read-out
Quartz window
Photo cathode
MCP stack
Resistive screen
other
pickup electrodes:
Read-out technique can easily be
reconfigured using the same detector
head.
Patented technique
Wedge&Strip, Pixel,…
Counting/Imaging VUV photons or particles with reconfigurable read-out
“open RS-PMT”
MCP stack
Resistive screen
pickup electrodes:
Image charge read-out has some
advantages over charge collection for
some anodes:
Beneficial even for open-face detectors
Patented technique
Delay-line,
Wedge&Strip,
Pixel,
…
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
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
y = (w - v)/√3
Example for x-layer:
x = u = - (v + w)
(vector addition)
v
(over-determination)
w
u
x = u
But how can this help
correcting non-linearity ?
50 mm LC Hex-DL on a 4-layer PCB
(no mask needed)
relative charge / %
Linearity correction
of LC-delay-line:
Experiment 4
(d=1.0 mm)
Gauss Fit
Xc=18.9 mm
140
120
100
s=0.86 mm
80
2,0 mm
60
40
20
of RS-PMT:
0
16
18
20
position / mm
22
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)
Object
in cooperation with Volker Dangendorf, PTB Braunschweig
Thanks to Jürgen Barnstedt from Tübingen for borrowing us his RS-PMT!
Results of Barnstedt et al. (1998)
25mm RS-PMT (Proxitronic)
- bi-alkali photo-cathode
- 4-jaw Wedge&Strip anode
Projection of grid mask 70/600micron, resolution 35 micron (1:700)