1. Goals of the Workshop The Development of Large-Area Psec TOF Systems
Henry J. Frisch
Enrico Fermi Institute and Physics Dept
University of Chicago
9/22/2018
Goals of the Workshop; Argonne

2. Goals of the Workshop; Argonne
OUTLINE
Goals of workshop
A little history of the project: why picosec, and why `large-area’? (This is the 7th Workshop!)
Description of concept- straw plan for concreteness, slings and arrows, education
Specific Questions to be answered.
9/22/2018
Goals of the Workshop; Argonne

3. Goals of the Workshop; Argonne
Create/connect a community to work on large-area photo-devices, especially those in material science, surface chemistry, photo-processes.
9/22/2018
Goals of the Workshop; Argonne

4. Goals of the Workshop; Argonne
Identify/collect technical details; find and understand state-of-the-art; identify facilities and resources
9/22/2018
Goals of the Workshop; Argonne

5. Goals of the Workshop; Argonne
Identify and describe possible `show-stoppers’ on the path(s) to large-area photo-detectors; assess risk of steps on path; Answer the question “Is there a reason why this won’t work?”
9/22/2018
Goals of the Workshop; Argonne

6. Goals of the Workshop; Argonne
Add resources and knowledge (i.e. people) to the growing collaboration working on the proposal; (we need a first draft very soon!)
9/22/2018
Goals of the Workshop; Argonne

7. Goals of the Workshop; Argonne
Modus Operandi so far
In Nov. 2005, we had our 1st workshop- idea was to invite folks working or interested in related subjects- didn’t know many (most) of them
Have developed tools and knowledge- also contact with pioneers and practictioners (Ohshima, Howorth, Va’vra,…; Breton, Delanges, Ritt, Varner)
Development clearly too big for one group- devices, electronics, applications- have worked collaboratively with each other, national labs (see talks by Karen, Andrew,Jerry,…), and industry (Burle/Photonis, Photek, IBM,…)-believe we have now solved the front-end electronics problem.
Now want to extend this inclusive model of creating a community into the device itself- hence this highly focused workshop.
9/22/2018
Goals of the Workshop; Argonne

8. Motivation, a little history-
Needs: HEP colliders, neutrino detectors, medical imaging (e.g. PET-TOF), accelerator diagnostics, truck/container scanners, …
Three key developments since the 60’s may allow us to rethink the possibilities: nano/material science, fast, cheap, low-power many-channel electronics, and powerful computation for simulation
Since the first workshop we have developed a readout scheme that is relatively insensitive to size- does not scale as area. Allows very large area detectors, so new applications.
Can optimize parameters for different applications based on time, space resolution, occupancy, geometry, and cost- however there are common features.
9/22/2018
Goals of the Workshop; Argonne

9. An Explanation of what follows
I’ve been driven by wanting to follow flavor-flow in colliders- most of our work has been focused on that geometry- light made in window by a relativistic particle, ~30 photo-electrons, goal of <= 1 psec timing. You’ll see most results for this regime- have to scale back to single photons (Jerry Va’vra is a notable exception)
However, this path has led us to solving the electronics problem for large-area detectors- the solution for timing turns out to solve the problems of readout for large areas (capacitance, among other things).
Note- good time and space resolution come naturally in this design- get 3D (`tomographic’) info by design. (time resolution IS space resolution- key point).
9/22/2018
Goals of the Workshop; Argonne

10. Goals of the Workshop; Argonne
GOAL: to Develop Large-Area Photo-detectors with Psec Time and mm SpaceResolution
Too small- can go larger-
(But how does multiplication work- field lines?)
From Argonne MSD ALD web page- can we make cheap (relatively) ultra-fast planar photo-detector modules?
9/22/2018
Goals of the Workshop; Argonne

11. Characteristics we need
Feature size <~ 300 microns (= 1 psec at c)
Homogeneity (ability to make uniform large-area- think amorphous semicndtr solar-panel)
Fast rise-time and/or constant signal shape
Lifetime/robustness/simplicity
Cost/unit-area << that for photo-multipliers
9/22/2018
Goals of the Workshop; Argonne

12. Goals of the Workshop; Argonne
Design Goals
Colliders: ~ 1 psec resolution, < 100K$/m2
Neutrino H2O: ~100 psec resolution, < 1K$/m2
PET: ~ 30 psec resolution, < 20% of crystal cost
Micro-photograph of Burle 25 micron tube- Greg Sellberg (Fermilab)- ~2M$/m2- not including readout
9/22/2018
Goals of the Workshop; Argonne

13. Goals of the Workshop; Argonne
Proof of Principle
Camden Ertley results using ANL laser-test stand and commercial Burle 25-micron tube- lots of photons
(note- pore size may matter less than current path!- we can do better with ALD custom designs (transmission lines))
9/22/2018
Goals of the Workshop; Argonne

14. `Photo-multiplier in a Pore’
Idea is to build a PMT structure inside each pore- have a defined dynode chain of rings of material with high secondary emissivity so that the start of the shower has a controlled geometry (and hence small TTS)
One problem is readout- how do you cover a large area and preserve the good timing?
Proposed solution- build anode into pores, capacitively couple into transmission lines to preserve pulse shape.
9/22/2018
Goals of the Workshop; Argonne

15. Large-area Micro-Channel Plate Panel “Cartoon”
N.B.- this is a `cartoon’- working on workable designs-join us…
Front Window and Radiator
Photocathode
Pump Gap
High Emissivity Material
Low Emissivity Material
`Normal’ MCP pore material
Gold Anode
50 Ohm Transmission Line
Rogers PC Card
9/22/2018
Goals of the Workshop; Argonne
Capacitive Pickup to Sampling Readout

16. Get position AND time Anode Design and Simulation(Fukun Tang)
Transmission Line- readout both ends=> pos and time
Cover large areas with much reduced channel account.
9/22/2018
Goals of the Workshop; Argonne

17. Photonis Planicon on Transmission Line Board
Couple 1024 pads to strip-lines with silver-loaded epoxy (Greg Sellberg, Fermilab).
9/22/2018
Goals of the Workshop; Argonne

18. Comparison of measurements (Ed May and Jean-Francois Genat and simulation (Fukun Tang)
Transmission Line- simulation shows 3.5GHz bandwidth- 100 psec rise (well-matched to MCP)
The time difference yields a velocity of 64ps/cm against 68ps predicted

19. Scaling Performance to Large Area Anode Simulation(Fukun Tang)
48-inch Transmission Line- simulation shows 1.1 GHz bandwidth- still better than present electronics.
9/22/2018
Goals of the Workshop; Argonne

20. Front-end Electronics
Critical path item- probably the reason psec detectors haven’t been developed
We had started with very fast BiCMOS designs- IBM 8HP-Tang designed two (really pretty) chips
Realized that they are too power-hungry and too ‘boutique’ for large-scale applications
Have been taught by Gary Varner, Stefan Ritt, Eric DeLanges, and Dominique Breton that there’s a more clever and elegant way- straight CMOS – sampling onto an array of capacitors
Have formed a collaboration to do this- have all the expert groups involved (formal with Hawaii and France)- see talks by Tang and Jean-Francois at Lyon
9/22/2018
Goals of the Workshop; Argonne

21. FY-08 Funds –Chicago Anode Design and Simulation (Fukun Tang)
9/22/2018
Goals of the Workshop; Argonne

22. Front-end Electronics
Wave-form sampling does well- CMOS (!)
9/22/2018
Goals of the Workshop; Argonne

23. Application to a water Cherenkov Counter- effect on the physics
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Goals of the Workshop; Argonne

24. Goals of the Workshop; Argonne
Application to a water Cherenkov Counter- effect on the physics- can you get much more physics bang for your buck? (and also save big bucks!)
What does coverage buy ?
What does spatial resolution in x-y buy?
Can x-y-z resolution allow track reconstruction?
Can x-y-z resolution allow pizero-electron sep?
Can one get momentum from multiple scattering?
What are the trade-offs in geometry if you have robust (pressure-resistant) detectors? (Mayly)
What haven’t we thought of? (e.g. magnetic field for sign determination).
9/22/2018
Goals of the Workshop; Argonne

25. Strawman Large-area Design “Straw” MCP panel
Use AAO to make 1” square active areas in a 64-element array in a single sheet of AAO
Use ALD to make coatings
Solve (?) ion-feedback problem by “hiding PC” from pore
Use small pores and “funnels to get large active area fraction
Use septa for current paths
9/22/2018
Goals of the Workshop; Argonne

26. Strawman Large-area Design “Straw” 2 foot square module
9 8”by 8” double panel stacks make a module
Transmission line readout covers full 24”
Electronics on the back side so you can tile up to larger modules
9/22/2018
Goals of the Workshop; Argonne

27. Goals of the Workshop; Argonne
Drafting a Proposal
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Goals of the Workshop; Argonne

28. Goals of the Workshop; Argonne
Drafting a Proposal
9/22/2018
Goals of the Workshop; Argonne

29. Specific Questions to Be Answered
3-yr R&D leading to a commercializable large-area device
Useful to try to make a resource-loaded schedule, even if it’s R&D with many unknowns
Need to identify check-points, risk
May need alternative parallel efforts for higher risk efforts
Application-specific design can grow out of 3-yr effort
9/22/2018

30. Specific Questions to Be Answered
3-yr R&D leading to a commercializable large-area device
Available for discussion, criticism, etc.- is intended only as a starting point to sharpen discussion- join us!
I am not an expert (tho not an excuse for making something like this)- there are many in the room who know at least some of this is nonsense- so be gentle and constructive- take it in the spirit offered, and make it better..
9/22/2018
ETC- (3 YRS)

31. Goals of the Workshop; Argonne
The End-
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Goals of the Workshop; Argonne

32. Goals of the Workshop; Argonne
Backup Slides
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Goals of the Workshop; Argonne

33. Anode Return Path Problem
Current out of MCP is inherently fast- but return path depends on where in the tube the signal is, and can be long and so rise-time is variable
Incoming Particle Trajectory
Signal
Would like to have return path be short, and located right next to signal current crossing MCP-OUT to Anode Gap
9/22/2018
Goals of the Workshop; Argonne
S R

34. Capacitive Return Path Proposal
Return Current from anode
Current from MCP-OUT
Proposal: Decrease MCP-OUT to Anode gap and capacitively couple the return (?)
9/22/2018
Goals of the Workshop; Argonne

35. The Future of Psec Timing-
From the work of the Nagoya Group, Jerry Va’vra, and ourselves it looks that the psec goal is not impossible. It’s a new field, and we have made first forays, and understand some fundamentals (e.g. need no bounces and short distances), but it’s entirely possible, even likely, that there are still much better ideas out there.
Big Questions:
What determines the ultimate limits?
Are there other techniques? (e.g. all Silicon)?
9/22/2018
Goals of the Workshop; Argonne

36. Smaller Questions for Which I’d Love to Know the Answers
What is the time structure of signals from crystals in PET? (amplitude vs time at psec level )
Could one integrate the electronics into the MCP structure- 3D silicon (Paul Horn, Pierre Jarron)?
Will the capacitative return work?
How to calibrate the darn thing (a big system)?!
How to distribute the clock
Can we join forces with others and go faster?
Saclay slide
9/22/2018
Goals of the Workshop; Argonne

37. Present Status of ANL/UC
Have a simulation of Cherenkov radiation in MCP into electronics
Have placed an order with Burle/Photonis- have the 1st of 4 tubes and have a good working relationship (their good will and expertise is a major part of the effort): 10 micron tube in the works; optimized versions discussed;
Harold and Tang have a good grasp of the overall system problems and scope, and have a top-level design plus details
Have licences and tools from IHP and IBM working on our work stations. Made VCO in IHP; have design in IBM 8HP process.
Have modeled DAQ/System chip in Altera (Jakob Van Santen); ANL will continue in faster format.
ANL has built a test stand with working DAQ, very-fast laser, and has made contact with advanced accel folks:(+students)
Have established strong working relationship with Chin-Tu Chen’s PET group at UC; Have proposed a program in the application of HEP to med imaging.
Have found Greg Sellberg and Hogan at Fermilab to offer expert precision assembly advice and help (wonderful tools and talent!).
9. Are working with Jerry V’avra (SLAC); draft MOU with Saclay
9/22/2018
Goals of the Workshop; Argonne

38. A real CDF event- r-phi view
Key idea- fit t0 (start) from all tracks
9/22/2018
Goals of the Workshop; Argonne

39. Why has 100 psec been the # for 60 yrs?
Typical path lengths for light and electrons are set by physical dimensions of the light collection and amplifying device.
These are now on the order of an inch. One inch is 100 psec. That’s what we measure- no surprise! (pictures from T. Credo)
Typical Light Source (With Bounces)
Typical Detection Device (With Long Path Lengths)
9/22/2018
Goals of the Workshop; Argonne

40. Geometry for a Collider Detector
2” by 2” MCP’s
Typical Area:
28 sq m (CDF)
25 sq m (LHC)
=>10K MCP’s
Beam Axis
Coil
Space in the radial direction is expensive- need a thin segmented large-area (30m2) detector
9/22/2018
Goals of the Workshop; Argonne

41. Small dim. Anode Structure?
RF Transmission Lines
Summing smaller anode pads into 1” by 1” readout pixels
An equal time sum- make transmission lines equal propagation times
Work on leading edge- ringing not a problem for this fine segmentation
9/22/2018
Goals of the Workshop; Argonne

42. Solutions: Generating the signal
Use Cherenkov light - fast
Incoming rel. particle
Custom Anode with
Equal-Time Transmission
Lines + Capacitative. Return
A 2” x 2” MCP- actual thickness ~3/4”
e.g. Burle (Photonis) with mods per our work
9/22/2018
Goals of the Workshop; Argonne
Collect charge here-differential
Input to 200 GHz TDC chip

43. Use Cherenkov light - fast
Generating the signal for relativistic particles (HEP, nuclear, astro, accelerator- but different for neutrinos)
Incoming rel. particle
Use Cherenkov light - fast
Custom Anode
Present work is with commercial MCP’s: e.g. Burle/Photonis Planicons. Expensive (!), hard to get, little flexibility.
BUT- it works. And well.
9/22/2018
Goals of the Workshop; Argonne

44. Starting Point- Time resolution
Resolution on time measurements translates into resolution in space, which in turn impact momentum and energy measurements.
Silicon Strip Detectors and Pixels have reduced position resolutions to ~5-10 microns or better.
Time resolution hasn’t kept pace- not much changed since the 60’s in large-scale TOF system resolutions and technologies (thick scint. or crystals, PM’s, Lecroy TDC’s)
Improving time measurements is fundamental , and can affect many fields: particle physics, medical imaging, accelerators, astro and nuclear physics, laser ranging, ….
Need to understand what are the limiting underlying physical processes- e.g. source line widths, photon statistics, e/photon path length variations.
What is the ultimate limit for different applications?
9/22/2018
Goals of the Workshop; Argonne

45. Benefit of TOF no TOF 300 ps TOF 1 Mcts 5 Mcts 10 Mcts
Better image quality
Faster scan time
1 Mcts
5Mcts
1Mcts
1Mcts TOF
5Mcts TOF
5 Mcts
10 Mcts
Slide from Chin-Tu Chen (UC) talk at Saclay Workshop
Karp, et al, UPenn

46. Time-of-Flight Tomograph
Slide from Chin-Tu Chen (UC) talk at Saclay Workshop
 x
Can localize source along line of flight - depends on timing resolution of detectors
Time of flight information can improve signal-to-noise in images - weighted back-projection along line-of-response (LOR) D
One normal variation in PET cameras is the “time-of-flight” or TOF design. By measuring the difference in arrival time at the two detectors, the positron source can be localized along the line of flight. Doing this does not improve the spatial resolution, but improves the signal to noise ratio (the mechanism will be described in more detail in the next slide) — the variance improves by a factor of 2D/ct, where D is the diameter of the radionuclide distribution, c is the speed of light, and t is the TOF resolution. Several TOF PET systems were built in the 1980’s with barium fluoride or cesium fluoride scintillators. They achieved ~500 ps timing resolution, which results in 8 cm localization. For objects the size of the human head (which was what most PET cameras imaged in the 1980’s) the net result is a tomograph with a factor of ~2 lower variance than a non-TOF BGO tomograph.
Problems arose from the use of barium fluoride as a scintillator. It is less dense than BGO, and so the spatial resolution is degraded. In addition, the wavelength of its fast emission is in the hard UV, which made it difficult to work with (i.e. expensive) because it does not penetrate glass-windowed photomultiplier tubes or any known glue (to couple the crystal to the photomultiplier tube). Finally, it was difficult to keep these cameras in tune. Thus, TOF PET largely died at the end of the 80’s. However, the advent of LSO and other new PET scintillators (that can provide excellent timing resolution without the material drawbacks of barium fluoride) makes TOF a promising direction for modern PET.
 x = uncertainty in position along LOR
= c . t/2
9/22/2018
Goals of the Workshop; Argonne
Karp, et al, UPenn

47. Goals of the Workshop; Argonne
TOFPET DREAM
30 picosec TOF
4.5 mm LOR Resolution
10 picosec TOF
1.5 mm LOR Resolution
3 pico-sec TOF
0.45 mm LOR Resolution
Histogramming
No “Reconstruction”
30-50 may be possible (LeDu)
Slide from Chin-Tu Chen (UC) talk at Saclay Workshop
9/22/2018
Goals of the Workshop; Argonne