16 August 2006 APD module development at IU 1 APD Module IU B. Adams, F. Busch, P. Childress, W. Fox, S. Mufson, J. Urheim, G. Visser with much input from: T. Chase, L. Mualem August 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

16 August 2006 APD module development at IU 2 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)

16 August 2006 APD module development at IU 3 Additional Requirements  Flip-chip mounting of APD on 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.

16 August 2006 APD module development at IU 4 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…

16 August 2006 APD module development at IU 5 APD Module: TEC side Heatsink holder Heatsink TEC glued here Water inlet/outlet Hole (1 of 2) in wall of heatsink for TEC leads

16 August 2006 APD module development at IU 6 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

16 August 2006 APD module development at IU 7 APD Module: Optical Connector

16 August 2006 APD module development at IU 8 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 surface Note o-ring. 2nd half of clamshell abuts this surface

16 August 2006 APD module development at IU 9 APD Housing/Heatsink testing cookie side with insulation removed APD housing assembly with insulation removed

16 August 2006 APD module development at IU 10 Understanding TEC & Heat Load  Keep Cold Side at 0 o 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

16 August 2006 APD module development at IU 11 RTDHeatsinkDiffAmpsVolts power I*V 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 = 5.5 W This can be done w/ near 15 C at ~2 cc/s Results w/ water-cooled heatsink

16 August 2006 APD module development at IU 12 APD Housing/Heatsink testing wet end of insulated APD test setup cookie end of insulated APD test setup.

16 August 2006 APD module development at IU 13 APD Housing/Heatsink testing Insulated APD housing test unit wrapped with foil.

16 August 2006 APD module development at IU 14 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

16 August 2006 APD module development at IU 15 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.

16 August 2006 APD module development at IU 16 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

16 August 2006 APD module development at IU 17 Manifold Snout / Cookie xface Manifold snout bottom piece end Groove for insertion of cookie Tab on cookie

16 August 2006 APD module development at IU 18 Glue Slot in Cookie (Tom C.)

16 August 2006 APD module development at IU 19 New Design for TEC Side Cookie Hole for alignment pin Spacer Frame Heat sink assembly

16 August 2006 APD module development at IU 20 New Heatsink & Holder Holder / Spacer frame (glued to carrier board) Heatsink assembly

16 August 2006 APD module development at IU 21 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…