16 august 2006 apd module development at iu 1 apd module development @ iu b. adams, f. busch, p....
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16 August 2006 APD module development at IU 1
APD Module Development @ IUB. Adams, F. Busch, P. Childress, W. Fox, S. Mufson,
J. Urheim, G. Visserwith much input from:
T. Chase, L. MualemAugust 2006 Collaboration Meeting, FNAL, - Electronics breakout
System Overview
Summary of Earlier Design / Thermal Testing Efforts
Developments Since Int’l Falls Mtg.
Open Questions
Plans for the Coming Months
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Requirements & Goals
Req’s for Photodetector Interface / APD Module Enclosure Optical Alignment:
Fibers must be aligned w/ APD pixels (both transversely & longitudinally)
I.e., module must serve as an alignment jig for “Cookie” holding the fiber-ends
Cooling:
APD’s must be cooled to -15 C
Environmental:
Must be impervious to leakage of light & humidity
Electronic Interface
APD signal, bias lines, thermal sensor, TEC power connections to FEB.
Our current goals: Finalize design so that production can commence on 500 enclosures for IPND… …in short term, fabricate 10 prototypes matched to prototype APD/carrier board
assemblies. …work on interface with scintillator module manifold snout (w/ T. Chase)
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Additional Requirements
Flip-chip mounting of APD on 0.060-in circuit board. We call this the “carrier board”. It has cutouts aligned w/ APD pixels.
APD is cooled directly by a Peltier Effect TEC. The TEC must not apply significant mechanical stress to the APD array
For this reason we deploy a deformable “crush pad” between TEC & APD
The hot side of the TEC is thermally connected to a heat sink +15 C water-cooling is the current baseline.
TEC mean time to failure: ~23 yrs, so failure rate = 3 / day ? The TEC’s will need to be swappable.
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Preliminary Design
“Clam-shell” design for APD Module Enclosure Injection-molded pieces surround (most of) carrier board,
creates gas volume to keep APD dry and dark, and limits heat conduction paths.
Our optical connector (“cookie”) is actually an entire 1/2 clam-shell. It will be permanently fastened to the scintillator module manifold snout The clamshell design simplifies alignment and establishment of a good
gas/light seal for environmental isolation The other half of the clamshell consists of a “heat sink holder” plus
“heat sink /epoxy /TEC /crushpad” stack assembly.
We have investigated both air- & water-cooled heat sinks Focusing on +15 C water, since that’s the current baseline…
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APD Module: TEC side
• Heatsink holder
• Heatsink
TEC glued here
Water inlet/outletHole (1 of 2) in wall of heatsink for TEC leads
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Prototype heatsinks
• Three of the prototype heatsinks used for testing.
Bored out aluminum stock - cheap to fabricate
Water inlet/outlet will be plastic - i.e., with cap will be a single injection molded piece
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APD Module: Optical Connector
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APD Module: Optical Connector
Hole for x-y alignment pin, matching holes in carrier board
Each line is actually two fiber ends, side by side
These surfaces are faced off together. Provides registration in z to APD side of carrier board
This design meets alignment specifications & minimizes heat conduction paths……but is not well suited for easy threading of fibers…
Carrier board sits against this surfaceNote o-ring.
2nd half of clamshell abuts this surface
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APD Housing/Heatsink testing
• cookie side with insulation removed
• APD housing assembly with insulation removed
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Understanding TEC & Heat Load
Keep Cold Side at 0o C Let heat sink temp float
See how much current needed to attain given T. Open circles are our data.
From this can infer Heat Load from TEC specs for this Tcold
This turns out to be ~0.55 W.
Also see how much power is consumed by TEC
For T = 30 C, this is about a watt
Of course heat load is different at -15 C
But TEC operates as advertized, at least at 0 C
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RTD Heatsink Diff Amps Voltspower
I*V
-15 0 15 0.76 0.88 0.67
-15 0.5 15.5 0.79 0.91 0.72
-15 3.5 18.5 0.88 1.03 0.91
-15 4.8 19.8 0.94 1.1 1.03
-15 6 21 0.98 1.15 1.12
-15 9.2 24.2 1.14 1.35 1.53
-15 9.3 24.3 1.14 1.37 1.57
-15 9.5 24.5 1.16 1.38 1.60
-15 9.7 24.7 1.16 1.38 1.60
-15 12 27 1.28 1.54 1.97
-15 15 30 1.60 1.93 3.09
-15 15 30 1.60 1.89 3.03
Aim to run APD at -15 C
TEC is ~linear in current required up to T = 30 C(see previous slide)
We measure 1.60 A for this configuration, thus heat load is ~2.5 W (see X on previous slide)
Must supply ~3.0 W to TEC
This means total heat to remove is 3.0 + 2.5 = 5.5 W
This can be done w/ water @ near 15 C at ~2 cc/s
Results w/ water-cooled heatsink
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APD Housing/Heatsink testing
• wet end of insulated APD test setup
• cookie end of insulated APD test setup.
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APD Housing/Heatsink testing
• Insulated APD housing test unit wrapped with foil.
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Impact of Insulation
3.4 Watts
2.7 Watts
Time (minutes)
3.2 Watts
Power into TEC
Full Insul’nNo Insul’nHalf Insul’n
Water flow 2cc/sec
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Developments Since Int’l Falls
Turn attention toward interface w/ manifold snout Meeting w/ Tom Chase at IU, June 27
o Holes versus Slots for fibers ? General threading considerations ?
o How to glue fibers ? (note: can use wicking glue if slots…)
o How to affix “cookie” to manifold snout ?
o Insulation issues ?
o Clearance issues ?
Suggestion that APD module should not be wider than depth of scint mdl.
o This means the carrier board width should shrink: 50.8mm --> 40mm
also reduces warping of board, beneficial for Hamamatsu for APD mounting
Aug. 2: receive suggestion from Tom for glue slot in cookie.
o Requires additional injection molded piece w/ hole pattern (see drawing).
Other developments Concerns for stresses to APD:
o Leads to notion of mylar tape “shim” applied to cookie after flycutting
o Also redesign of heat sink holder: add’n of IM spacer frame & modifc’n
heat sink (holder) to set height of TEC.
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New Optical Connector (Walt)
Shims would go here
Note: cookie is no longer “deep”, for ease of threading.
Potential thermal impact of this is unknown
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Manifold Snout / Cookie xface
Manifold snout bottom piece end
Groove for insertion of cookie
Tab on cookie
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Glue Slot in Cookie (Tom C.)
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New Design for TEC Side
Cookie
Hole for alignment pin
Spacer Frame
Heat sink assembly
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New Heatsink & Holder
Holder / Spacer frame(glued to carrier board)
Heatsink assembly
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Plans for the coming months
Prototype fabrication
Aim to build one or two prototypes now for thermal studies
Once we get APD/carrier board assemblies from Hamamatsu, plan is to machine ~10 to be distributed.
A new technician, Fritz Busch, has joined our group & will help with this effort.
Outstanding questions Desiccant
Must keep relative humidity to 3.4% to avoid condensation!!
But where to put desiccant and associated install’n issues…