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

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5(7) electronic channels only easy read-out

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Center-of-mass averaging

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high position resolution time resolution: < 1 ns Our typical resolution: 40-50 μm rms

80 mm “Hexanode” delay-line detector (patented)

Electronic readout:

T

ime-to-

D

igital-

C

onverter:

(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 5 mm grid constant, 1 mm obstacle NASA test mask 0.15 mm FWHM 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 Read-out technique can easily be reconfigured using the same detector head. Patented technique Quartz window Photo cathode MCP stack Resistive screen other pickup electrodes: Wedge&Strip, Pixel,…

Counting/Imaging VUV photons or particles with reconfigurable read-out

“open RS-PMT”

Image charge read-out has some advantages over charge collection for some anodes: Beneficial even for open-face detectors Patented technique MCP stack Resistive screen pickup electrodes: 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 Example for x-layer: x = u = - (v + w) (over-determination) (vector addition) v w u x = u But how can this help correcting non-linearity ?

50 mm LC Hex-DL on a 4-layer PCB

Linearity correction

of LC-delay-line: (no mask needed) of RS-PMT: 60 40 20 0 140 120 100 80 16 2,0 mm 18 20 position / mm Experiment 4 (d=1.0 mm) Gauss Fit X c =18.9 mm s =0.86 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) 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)