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Thermal Testing of TOB/TEC Hybrids at UCSB

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The CMS detector will run at –20 C in order to lessen radiation damage to the silicon

Why Thermal Test?

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Why Thermal Test Hybrids?

Some Hybrids fail at –20 C– APVs do not output– Hybrid fails to initialize– Noise increases in cold

(peltier current?)

APV: Analog Pipeline Voltage Mode Chip

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The 4 Hybrid Cold Box

Cold box design and photo courtesy of:Cold box design and photo courtesy of:Bruno Wittmer and Giacomo Squazzoni Bruno Wittmer and Giacomo Squazzoni @ CERN@ CERN

How to thermally test hybrids?How to thermally test hybrids?4 at a time.4 at a time.

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The Set-up at CERN

Picture courtesy of CERN

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The Set-up at CERN

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A question at Tracker weekConclusion

Hey folks, is there someone willing to test hybrids on a

large scale?!?!…

Hey folks, is there someone willing to test hybrids on a

large scale?!?!…

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Building our own

ConstructionConstruction

&&

RepairRepair

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Slow Control

First order of business: hooking things up

• 5 temperature sensors• 1 humidity sensor

• 1 Water Flow Sensor• 1 Air Flow Sensor

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Interfacing to a PC: ACDCInterfacing to a PC: ACDC

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Cooling Down

Cooling Mechanism: Peltier Unit

Supercool Peltier:-Voltage = 28 V- Current = 13 A- Power = 350 W

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Cooling DownHow long should/does it take to get to –20?

Cold chamber

Peltier + PlateChiller

KTB 283

CT

AirKTS 295

Air Flow(0.05 L/min)

Water Flow (14 L/min)

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Simplifying things

)(8.4300 CBC TTK

WWP

hkxTTS

P SCI 1

)(

S= surface area of enclosure (m )k=thermal conductivity of walls (W/m C)h=convection factor (W/m C) x=thickness of walls (m)

2

2

CT BT

ST

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Simplifying things

Assumptions:1) Most of the heat transferred to the system goes into cooling the aluminum peltier plate (specific heat of aluminum is much greater than that of air)

dt

dTmc

dt

dQ m= 2.0 kg

c= 910 J/kg C

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Simplifying thingsAssumptions

2) The convection factor can be calculated by waiting until the system comes to equilibrium

CI PP

hkxTTS SE

1)(

)(8.4300 BE TTK

WW

ET Temp at equilibrium

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Simplifying thingsWaiting… (I was too impatient to wait for t )

CTE21

h= 7.55 (W/m C)2

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Calculating time to -20

CTmchk

xTTS SC

1)(

))(8.4300( CB TTK

WW

First order linear differential equation:

Solution: (T(t=0)=295K)

KKetT tC 9.2515.43)( )0045.0(

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Not quite…Calculation says that plate should reach –20 in ~14 minutes.

Actual time: ~21 minutes

Possible problems: • Unaccounted heat influx through leaks or grounding strips connecting plate to outside• assumptions made are flawed• Missing term in differential equation

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-20 Reached: On to Testing-20 Reached: On to Testing

Set-up in Clean RoomSet-up in Clean Room

ChillerChiller

Cold BoxCold Box

PC for MonitoringPC for Monitoring+ Controlling+ Controlling

ElectronicsElectronics

Gas/Water Flow ControlGas/Water Flow Control

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Testing Software: ARCSTesting Software: ARCSAPV Readout Control SoftwareAPV Readout Control Software

CommunicatesCommunicatesWith ACDC With ACDC via TCP/UDPvia TCP/UDP

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What are we testing for?Shorted channels: On each clock, charge injected into every 8th channel. Shorted channels share, ADC amplitude is diminished.

128 Channels per APV-6 APV hybrids: 768-4 APV hybrids: 512

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What are we testing for?

Open Channels:Open Channels:Inject charge Inject charge throughthroughCapacitive coupling Capacitive coupling of pitch adapter to of pitch adapter to antenna carrying antenna carrying TTL PulseTTL Pulse

AntennaAntenna

Pitch AdapterPitch Adapter

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AR

C

NIMpulsertr

igge

r NIMto

TTL

start

out

50“antenna” very close (~1mm) to the bond pads

Peak - InvOFF Pulser ON Peak

Mode Optimal

latency

OPENS

Easier said than done

Slide courtesy of G.Squazzoni

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We thought it was the pulser

ARC BoardLVDS

NIM LogicNIMTTL

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LVDS Signal?

• ARC Boards with

functioning External Bus– Ser 29– Ser 31

• ARC Boards with

non-functioning External Bus– Ser 56– Ser 57– Ser 59

LVDS Signal

Noise

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ARC Controller Problem

• Bad Batch of ARC BOARDS: LVDS Driver and LVDS Receiver U32 and U33 were switched during board assembly. Problem was never discovered.

• External Buss connector and associated IC’s on lower left of photo. U32

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With Pulser Operational…

• Opens detectable in “Scope Mode” Intentionally Plucked Bonds Show up in Pedestal Profile

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With Pulser Operational….

• Opens are also detectable in Pedestal & Noise Test

Plucked Bonds

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Grounding Issues

Same Problem CERN was having….

Huge spikes in noise at APV edges

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Grounding•Ferrite Ring around Coax

•G10/copper strips connect peltier plate to front end ground

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Much Better

Old Grounding

New Grounding

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Thermal Cycle Test

“One Button” test

Three Sets of Tests:

• Pedestal & Noise

• Pulser

• Short Detection

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Automated Test ResultsFinal Report After Thermal Cycle Test:Lists -Shorts -Opens -Noisy Channels

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The testing goes on…

So far, about 100 hybrids have been thermal cycled.

At maximum capacity: ~28 per day

And the cycling will continue…