ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Performance of the multi-channel Hybrid Photodiodes for the CMS HCAL Professor Priscilla Cushman University of Minnesota The US-CMS HCAL Collaboration Fermilab Florida State Purdue Notre Dame University of Illinois (Chicago) University of Mississippi University of Maryland Rochester University of Minnesota

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota HCAL The CMS Tile/Fiber Hadronic Calorimeter HB HE HO

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Reading out the Towers of Tiles with WLS fiber and HPD’s 4 Tesla Magnetic Field

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota The CMS Hybrid Photodiode DEP Tube Fabrication by Delft Electronic Products (Netherlands) Subcontracts: Canberra (Belgium): diodes Schott Glass (USA): fiber optic windows Kyocera (Japan): vacuum feedthru/ceramic carrier 19-channels 5.4mm each 12 kV across 3.3 mm gap with V th Gain of  m Silicon PIN diode array, T-type, 80 V reverse bias PIN Diode array Ceramic feedthrough Fiber-Optic Window Photocathode e

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Larger active area: Less room for HV connection, possible field distortions Minimize gap: Improve tube components This has been a development project This has been a development project (the tube) HV coax cable : Reliability and compatibility with RBX RBX mountings and cookies must be rubber insulated Gold-plated pins: Enables us to use ZIF sockets - questions of gold diffusion FIBERS Plate HPD Plate Cookie Ring HV Cable Electronics Interface Board

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Custom Pixel Design: 19 ch (towers) and 73 ch (short stacks) This has been a development project This has been a development project ( the diode) 2 side-contacts (100 nm thick Al) Bump-bonded vacuum feedthru n++ contact n++ p+ n+ bulk (200  m thick) AR (16 nm sputtered Si) Metal (25 nm AL) Barrier (25 nm SiO 2 ) Higher pinout density: wire-bonds =>glass feedthrus => ceramic from Kyocera Alignment to 50  m: manufacturer tolerances tightened, new measurement procedures Improved rise time: Thinner silicon: 200  m replaces 300  m Guard ring and drain structure: lower leakage current and better uniformity for edge pixels Lower depletion voltage and better control of process: higher breakdown voltage Surface aluminization and edge traces: Reduce negative crosstalk: 300  /sq => 1.7  /sq Antireflective coating: Reduce positive crosstalk from reflected light

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota 300  m thick200  m thick Pulse width can be shortened by reducing wafer thickness d or by increasing bias voltage, V b Drift time is approximately given by and the shape of the plateau mirrors the internal electric field

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota AC Crosstalk eliminated by Aluminization and edge traces Pixels in center row Positive crossstalk now observed !

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota photoelectrons Light Re-emitted photoelectrons APD views reflected light pe backscatter focussed by B Light injected thru fiber Test Confirms Reflected Light produces optical crosstalk DIODE ARRAY FIBER OPTIC & PHOTOCATHODE

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Study Problem at Minnesota, then export technology to DEP IMD - optical modeling package for multilayer structures (by David L. Windt, ) Model Data monochrometer PIN diode Samples: glass slides with various coatings (PECVD) 10 nm Ag 120 nm SiO 2 8 nm A-SiH 15 nm Ag 50 nm SiO 2 16 nm A-SiH 25 nm Al 25 nm SiO 2 Some Options Minnesota test slides 14 nm a-SiH 25 nm Al 25 nm SiO 2

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Quality Assurance: Can process 40 tubes/month failpass Return to DEP Bake-out at 10 kV for 2 weeks Evaluate >600 tubes, automated procedure, complete web-accessible database Alignment measurements for 50 micron tolerance Leakage current for each pixel and guard 80V 2-D response scans (10kV, 80 V), HV gain, bias curve crosstalk checks alignment DC Station Machine custom ring Single pe spectra per pixel To FNAL for installation in readout boxes Viking Station Lifetime: Q, Cf 252, HV High Rate and B-Field tests subset DC crosstalk Optical xtalk in each pixel in B-field. AC crosstalk Recorded scope traces of AC xtalk for nn pixels capacitance vs bias Cap Station

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Samples from DC Station Pixel Number Dark Current e e e e e e e e e e e e e e e e e e e-009 Total Current e-007

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Precision Registration Test fixture = Standard Mount + metal plate with 3 alignment holes Scan to find centroid of alignment holes Same scan finds pixel intersections above and below metal piece by iterative sector equalization Machine shop uses measured  x,  y,  to produce Custom Ring Each ring is registered to its HPD via alignment pins such that Readout Module and Cookie (Notre Dame and FNAL) can be universal Stabilized light source HPD Mount Scanning Table Integrating sphere Focussing optics Green filter Metal alignment plate FIBERS Plate Alignment Pins Plate HPD Ring HV Cable Electronics Interface Board

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Initial Alignment ScanFinal Alignment Production # SQRT(dX2 +dY2 +dTheta2) Alignment Procedure to 50  m is effective 50 microns

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota AC Station: Viking chip serial readout at 10 MHz HPD + interface card AC-Coupling 2 chip 128 channel PA Repeater card Laptop with ADC card 128 Multiplexer Shaper Sample & hold 10 MHz readout

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Individual spectra for each pixel from AC Station 19-channel tube at low light levels

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota AZ HPD List Search Results HPD Serial Number DateTimeQE at 480 QE at 520 QE at 560 Global Status AZ :10:48null Failed AZ Bias Curve Search Results HPD Serial Number Scan DateScan TimeHigh VoltageData FileBias CurveStatus AZ :35:45739BV(2C)AZ datAZ bvgraph.gifPassed AZ Dark Currents Search Results HPD Serial Number Scan DateScan Time Bias Voltage High Voltage Summed Current Pixel Current Bias Current Data FileDCGraphStatus AZ :43: e e e-09DCAZ dat AZ dc graph.gif Passed AZ Viking Search Results HPD Serial Number Scan DateScan TimeViking FilePixelsStatus AZ :09:40az VIK.rawAZ vikgraph.gifPassed AZ High Voltage Curve Search Results HPD Serial Number Scan DateScan TimeBias VoltageData FileResponse CurveStatus AZ :44:1080HV(2C)AZ datAZ hvgraph.gifPassed Database

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Tracking and Grading Procedures Grading is done through the database Contract specifications for each test must be met. Failing one test  Tube returned to DEP Trending Plots show specification compliance vs time (see following plots for examples) Excel spreadsheet updated and ed to CERN financial monthly Only pay for the cumulative number of approved tubes

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Spec: R < 3 Ohms Resistance in Ohms AC x-talk Spec:  pixels/input pixel < 3% Production # % of input light Silicon resistivity and aluminized traces now under control DEP now requires testing resistance of the aluminized traces before releasing the tubes readout 8 and 18 Illuminate center pixel 1 2 3

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota DC x-talk Spec:  Pixels/Input Pixel < 4%  % of input light Anti-reflective coatings are reasonable HPD Permanent 0.3 T field isolates optical crosstalk from backscatter. magnet illuminated pixel Production #

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Lifetime under HV and Light PIN reference diodes 1.0 mm diam. WLS fibers Blue LED’s Pixel 11 HPD Pixel 9 Lifetime Monitoring Stations monitor current (PIN diodes, HPD) and temperature Integrated Charge: (10 CMS years = 3 C over 25.6 mm 2 pixel at high  Expose to accelerated rate: Pixel 9 at 327 nA plus control pixel at CMS rate: Pixel 11 at 37 nA Surface scans done before and after exposure distinguish between photocathode degradation and silicon damage.

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Light off Light Steady Light injected into 2 pixels. Run over more than 2 years 3.4 C 0.4 C 13.7 C 1.6 C 19.1 C 2.2 C Integrated Q pixel 9 pixel 11 Pixel (led) – Pixel 10 Pixel 10 Percent change in response (gain*QE)

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Radiation Damage Radiation Damage: (10 CMS years = 5 x n/cm 2 in worst region) Expose samples to Cf : Oak Ridge: Early HPD version to n/cm 2 Remote operation at very high flux Monitor current, characterize before and after irradiation Result: No change in gain up to 5x10 12 n/cm 2, Monotonically increasing leakage current consistent with silicon Still worked even at 10  A of leakage current! 2001, 2003: Minnesota: new HPD to >10 11 n/cm 2 Low flux drawer instrumented similar to Lifetime Test Light injection, in situ gain curves, reference diode Result: Leakage current will rise at rate of 7 nA/yr in the worst location

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota 2004 Test Beam at CERN HO HB HE ECAL HO beam Wedge tests going on now

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Tracking a single channel in 4 Readout Modules Occasional changes in LED levels The PIN diode for HB1 flaked out for a while The HV was changed from 8kV to 10kV Two Months of operation at the test beam – monitored by led

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota HO Response to Muons: Select high Gain*QE tubes and run at 10 kV Ped. RMS Peak – Ped pe S/N Ring fC 5.0 fC ~18 pe 5 Ring fC 3.7 fC ~13 pe 4 Ring fC 2.5 fC 9 pe <3

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Special layer-by-layer readout for the testbeam shows Longitudinal Development of a 150 GeV Pion shower in HB HCAL alone HCAL + ECAL layer Barrel section (HB) will be run at 8 kV for stability & lifetime

ICHEP – Beijing, China Aug 16-22, 2004Professor Priscilla Cushman, University of Minnesota Conclusions 8 years ago, no existing technology could satisfy our specifications. Development project was initiated with one Company - DEP with backup plans which included Hamamatsu and Litton Quality Assurance from the start can discover unanticipated problems timely feedback creates new solutions – specifications may change Our yield under new specifications is only 60% but graded under original specs, it is closer to 80% Photosensor fulfills all CMS HCAL requirements as well as lifetime, stability, and operation in radiation field. They are currently operating as expected in the Test Beam All tubes will be manufactured and tested by February 2004.