Argonne National Laboratory is a U.S. Department of Energy laboratory managed by U Chicago Argonne, LLC.

• 2nd Measurement – Feb., 2011– Test board with individual components– 188 MeV protons– Discovered: LT1681 Controller Chip

trips & restarts

– Diode conducts at cold start– Diode is back biased– SEUs still happen, but recovery is fast

The TileCAL Low Voltage System

Radiation Testing Methodology

Measurements & Results

• Power for TileCAL Front-End Electronics• Novel Switching DC-DC Power Supply– Custom, Compact, High-Efficiency, 250 Watt– 8 Different Voltages Customized Bricks– Water Cooled; System Interface & Monitoring– Environment: Magnetic Field, Radiation Tolerant• 256 boxes on detector, 2048 bricks, + spares Reliability is Important Infrequent Access

End of Long Barrel Detector Section

LVPS Access

on Detector Drawer Electronics

LVPS Box8 bricks per Box

LVPS Brick

Single Event Upset Energy Dependence In a Buck-Converter Power Supply Design

Bruce Mellado2, Anusha Gopalakrishnan1, Sanish Mahadik1, Robert Reed2, Abhirami

Senthilkumaran1 1 - University of Wisconsin-Madison, Madison, WI USA

2 – The University of the Witwatersrand, Johannesburg, SAOn Behalf of the ATLAS Tile Calorimeter System

Gary Drake, Member IEEE, James Proudfoot

Argonne National Laboratory, Lemont, IL USA

• The Fix – Soft Start not used in brick operation– But, circuit does control startup rate Want capacitor for cold start Want capacitor out of circuit for normal operation Add a diode & resistor:

• Radiation Tolerance Requirements– 10 Years of Running, L = 1034 cm-2 sec-1

• 1st Measurement – Dec., 2010– Bricks tripped from SEU– 188 MeV protons

SEU Problem

We have performed a study of the susceptibility to Single Event Upsets (SEU) on the new upgraded supplies

TID (Grays)

NIEL Fluency (neutrons/cm2)

SEE Fluency

(protons/cm2)3.78 2.74x1011 6.74x1010

• SEU Testing Program– Proton beam at Mass. Gen. Hospital– 20 – 200 MeV protons– Read out continuously during irradiation

Soft-start capacitorExternal component

Value controls startup delay

Schematic

LT1681 Block Diagram

Soft Start Feature

• A Puzzle– SEUs not seen in earlier tests at 60 MeV– Why?...

• 3rd Measurement – Apr., 2011– Fix installed on 3 bricks– No more trips!

• 4th Measurement – Apr., 2012 Study SEUs as a function of energy

– 60 MeV, 80 MeV, 100.5 MeV, 140 MeV, & 216 MeV– Results: See energy dependence

Test Setup at MGH

Test Setup Configuration

Block Diagram of Brick

• Theory: Bendel Parameters [1] – In general, SEU susceptibility depends on fab tech., feature size, layout, and configuration

– Bendel Parameters: Parameterization of form:–Our fit:

[1] W.J.Stapor, et al., IEEE Trans Nucl. Sci., Vol. 37, NO.6, pp. 1966-1973, December 1990.

ToELMB(Control

Interface)

Startup

Shutdown

Opt

oIs

olat

orO

pto

Isol

ator

MonitorVoltages

VIN* IIN*

LT1681Controller

Chip

+

Vout

-

FETDriver

RSHUNT

VFB

IFB

Tran

sfor

mer

GNDSECGNDPRI

Startup&

ShutdownControl

OVP, OCP,

Temp, &

Monitor

RSHUNT

LC Filter

+

200V

-

LC Buck LC Filter

OpAmpRunStop

Over Temp

VOUT*

IOUT*

PR

IP

ower

SE

CP

ower

+VSEC

-

+VPRI

-

Isolated SecondaryPrimary

SEMI-EMPIRICAL 2 PARAMETER FIT