PositionSensitive MCP detector Personnel Mr Blake Wiggins graduate student Davinder Siwal RdS PI Indiana University Whether detecting photons neutrons or ions ultimately one is inevitably dealing with electrons ID: 617729
Download Presentation The PPT/PDF document "Neutron Imaging with a Novel" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Neutron Imaging with a Novel Position-Sensitive MCP detector
Personnel : Mr. Blake Wiggins (graduate student), Davinder Siwal, RdS (PI), Indiana University
Whether detecting photons, neutrons, or ions ultimately one is inevitably dealing with electrons.
Goal: Develop a detector with single electron sensitivity that has sub-millimeter position resolution, sub-nanosecond time resolution and the capability of resolving two spatially separated, simultaneous electrons.
Individual gunpowder grains inside a bullet
A motorcycle engine
Good position and time resolution are necessary in high quality imaging!
Neutron
imaging
Courtesy of PSI
A.S.
Tremsin
et al., NIM A652 400 (2011)
National Nuclear Security Association Award
No. DE-NA0002012 Slide2
Millions of leaded glass tubes 2-10
μm in diameter act as secondary electron emittersApplied voltage results in an electron producing an avalanche with typical amplification of approximately103 per plateSensitive to electrons, photons, ions
Commercially available PS-MCP technologies
CMOS Timepix detector (state-of-art)
While this approach achieves a resolution of 45-55 m FWHM, it has the disadvantages of:
Complex readout electronics (ASICs) – charge integrating approach
Limited size (tile 22 mm x 22 mm active area using 4 chips)
High power consumption (~1W/chip)
Helical delay line ; Resolution (FWHM): 60 µm; Cons: Fragile
Resistive anode; Resolution (FWHM) : 100-200 µm; Cons: Rate limit 100 kHz, double-hits
D
ue to its large amplification and sub-nanosecond time response the
microchannel
plate detector is an ideal tool for amplifying the original signal.
Hamamatsu Photonics K. K.,
Photomultiplier Tubes Basics and Applications 3
rd
ed
(2007).
Principle of OperationSlide3
Fast signal
Simple readoutMulti-hit capabilityLow power consumptionSenses (does not collect) the electron cloud
Introduction
to the Induced Signal
Approach
R. T.
deSouza
et al
, Rev. Sci.
Instrum.
83
, 053305 (2012). A single electron is amplified to
a cloud of 107
-108
electrons
and sensed
by 2 orthogonal wire
planes.
Wires in a sense wire plane have a 1 mm pitch and are connected to taps
o
n a delay line.
Position is related to the time difference between the signals arriving at the ends of the delay line.
Resolution (
m)
unoptimized
~ 500
Optimize bias, grounding
~240
Improve
zero crossing extraction
~115Slide4
Testing the Induced
Signal
Approach
By digitizing the signals at 10 GS/s and utilizing digital signal processing techniques, a position resolution of
95 m (FWHM) has been obtained
.
With the basic characteristics of the detector determined we turn to neutron detection …
S
ingle alpha particle incident on aluminized
mylar
foil ejects 2-7 electrons
Electrons are accelerated by an electrostatic field towards the position sensitive MCP
Following amplification by the MCP, signals from either end of the delay line are amplified by x30 and the waveforms are digitizedInsertion of a mask just in front of MCP allows determination of the position resolution
Resolution at (near) the single electron limit!Slide5
Low Energy Neutron Source (LENS) at Indiana University
13 MeV proton linac driver9Be(p,n) to produce neutrons
Thermalization (polyethylene, solid CH4
@ 6.5K)100 n/(ms.cm2)
20 Hz repetition rate
XY
Anode
Cd Mask*
* 2mm
Wide
Slits,
Horiz
.
Oriented, 5mm Pitch
σ(thermal) for
113
Cd = 19,820 b
10
B + n (25
meV
)
7
Li +
4
He
σ
= 3840 b
By inserting a neutron sensitive MCP (B-doped) in front of the Z-stack MCP, the detector becomes sensitive to thermal neutrons.
Slow Neutron Radiography
Efficiency for detection of thermal neutrons 20-50%Slide6
Detector setup
25 mm diameter Boron doped MCP (Nova Scientific) in front of a 40 mm diameter detection grade Z-stack MCP (
Photonis
)
Detector housed in ISO200 6-way cross
Dedicated oil free pumping P=2 x 10
-7
torr
NIM bin for HVPS, amplifiers, and trigger
Setup is compact and transportableSlide7
First Neutron images (Dec. 2016)
Count
rate (cps)
radiogenic decays i.e. bkg.
101
slow neutrons + bkg.
172
S/B = 0.7
Outline of 40 mm Z-stack and 25 mm B-doped MCP visible
Three horizontal slits clearly visible (limited by 15 mm diameter beam)
Unexpected intensity modulation in the x-direction
LENS at 10% power
Using VME based DAQ Caen V1729A (
max rate 300 Hz
)
2 mm wide horizontal slits spaced by 5 mmSlide8
Resolution of first Neutron images (Dec. 2016)
The measured resolution is a convolution of the intrinsic resolution of the detector with the finite slit width.
We represented the finite slit width as a step function with a 2 mm width and the intrinsic resolution as a Gaussian with an intrinsic width.
By varying the intrinsic width, the impact of the finite slit width can be determined.
Peak
Slit Width
FWHM
(mm)Instrinsic Rs
FWHM (mm)A2.130.906 B
1.810.770
C2.13
0.906
Fundamental limitation is S/B!To improve the S/B we need a higher neutron flux which requires a faster DAQ !
Average intrinsic resolution is 860 µm for the 2 mm slitsSlide9
Development of a high speed Neutron DAQ
AlazarTech
ATS9373 Waveform Digitizer:
2 Channels
2 GS/s sampling for 2 channels and 4 GS/s sampling for 1 channel
12 bit resolutionFixed +/- 400 mV Range
6.8 GB/s
PCIe x8 Gen 3 interface1.0 GHz analog bandwidth
Variable frequency external clockingSlide10
Characterizing the
nDAQ
Re-triggering capability and neutron pileup
Re-arm window
(system inhibited)
t = 128 ns
Digitization window
t = 128 ns
Max rate achieved with
pulser
:
200 kHz (includes recording to disk)
4 waveforms/event
400 MB/s (at ~ SSD limit)
1.1 MHz (w/o
recording
i.e. attainable with FPGA processing)
T= 20K
D= 10m
Slow n
The digitization and re-arm window result in a time interval during which neutron pile-up can occur
For 256 ns the pileup probability is 1 in 10
5
Even when it occurs, it can be distinguished by the multi-hit capability of the detector.Slide11
Alpha testing with
nDAQ
(asynchronous data)
Max rate of 9 x 103
cps measured. This rate is limited by source intensity (10 µCi
241Am)
Slits in mask (355 µm wide, 2 mm pitch) are clearly visible along with 1mm diameter holes
A relatively uniform background is observed for the MCP detectors
3.5 mm slits; 4mm pitchSlide12
Discussion of Results
Projection of slit spectrum indicates a measured spatial resolution of 603 µm (FWHM)
Deconvolution
of finite slit width yields an intrinsic resolution of 551 µm (FWHM)
This ”intrinsic” resolution includes the influence of slit scattering at the slit edges.
Maximum non-linearity
~1.4%;
average non-linearity ~0.6%
The increased intensity at the intersections where there are a lot of edges indicates that slit scattering significantly impacts the resolution.Slide13
Designed and realized a position sensitive neutron detector
Measured first neutron 2D image using induced signal approach. Initial resolution : ~860 µm (FWHM) with S/B of just 0.7Developed fast PCIe based DAQ (200 kHz/4 waveforms; 128 ns); ~103 speed-up
Spatial resolution (alphas) improved to 551 µm (FWHM
) with good linearity without optimization
Accomplishments/Summary
Outlook
Test with neutrons (LENS at full power) in summer 2017 using new
nDAQ
Develop multi-hit TDC for time-stamping for dynamics (underway)
Implement DSP routines in FPGA to achieve higher data rates
Propose run at LANSCE in 2018 (discretionary time earlier?)
Improved the intrinsic resolution for electrons: 115 um
to
95
um
Submitted
manuscript on PS
ExB
detector
for beam
imaging at RIB
facilities
Slow neutron imaging
I
maging