D.F.A DORMITORY

Under Construction

The purpose of the DFA Dormitory is to provide a safe area where detectors can be temporarily stored under bias voltage in a controlled environment. Long term leakage current will be monitored so that high leakage detectors can be culled out. The dormitory system was placed in operation in late October 1997 with an initial run with 5 separate fully bonded DFA's. The initial test run covered a span of 7 days with detectors biased at 60 volts. Future DFA burn in voltages will use the operating voltage as established by Pisa typically in the area of 40 volts. . The bulk and the guard ring leakage currents are monitored continuously during the period.

DFA Dorm Stack

Here is a photo of the 6-dorm stack showing the separate power supplies connected to the individual dorm chambers. The box at the top left holds the temperature/ humidity sensor along with signal conditioning which has a sample of the dormitory dry air routed to it. The small box at the bottom of the rack is the dorm interface into which all of the sense lines from the dorm chambers connect. A 50-conductor ribbon cable (from which the box is hanging) connects back to the National Instruments Data Acquisition board, which is mounted in the PC. The gauges on the upper right of the stack are used to monitor the flow and pressure of the dry air into the dorms. The dorms are powered by separate HP E3612A power supplies with a range of from 0 - 60 vdc / 0 - 120 vdc with 0.1v resolution and a 2mA minimum current limit employing a digital voltage and current display with independent adjustment on voltage 0 < V < 60 vdc with 0.1 vdc resolution

This photo shows the separate bias supplies feeding separate dormitory enclosures. (The light-tight anti-static DFA storage enclosures are set above the dorms)

Dry air supply with environmental monitoring, air supply will circulate through each DFA enclosure venting into a main enclosure which can be opened to gain access to each of the DFA enclosures.
Continuous monitoring of guard and bulk currents 0 < I < 220 uA with 120 nA resolution
Current limiting at 220 uA with slow voltage shutdown provisions
Battery backup for evening shutdown during power failures
Continuous display of all DFA bias currents, the typical sample period is 2 seconds as set by a virtual front panel control as illustrated in the sample virtual instrument front panels.
Independent light-tight housings to hold ring frames

Silicon Detector positioned in Dorm (note bias connector on left)

LabVIEW Controller with LabPC + general purpose I/O Board in a Network PC

Main Screen for Dorm Monitoring System

The Virtual Instrument (vi) Main Screen displays a bar chart illustrating the real-time bias currents for the detectors currently under test showing a bar stack of the guard and bulk and the sum currents. Controls are provided to set the sample rate and critical current alarm. . On the right hand portion of the screen the temperature and humidity time histories are displayed as a strip chart display. View the real time data collection by clicking here. The green status lights shown on the Main Screen Panel indicate which dorms are currently having data logged.
Individual DFA Dorm Monitoring Screen

The Individual Screens display the time history of the bias currents and the applied voltage. View the real time data collection process on a sample part by clicking here. The DFA part number and the test start time is also displayed. The sample rate of the data collection can be adjusted from this front panel. Data from this vi is collected every hour into an Excel spread sheet file for post analysis. The data records show the time history of all of the monitored parameters.

Signal conditioning (DFA Dorm Electronics Schematic) for the leakage current measurement consists of a voltage measurement across a 10k-ohm series resistor to provide the required current resolution. Detector current is limited by a 1N5283 200 uA constant current diode (replaces R5 in the attached schematic). The 1N5245 15 volt zener diodes provide over voltage protection for the analog to digital converter. The 8 channel multiplexer U1 provides for low data rate acquisition of DFA operating voltage data. Data collection is accomplished using the National Instruments PC-LPM-16PnP General purpose I/O Board which provides 12 bits of resolution digitized over a 5 volt range with 16 separate analog input channels. . This provides for 36 mV of resolution for the operating voltage and 120 nA of leakage current resolution.

Dorm Parts List

(Last update on 3/4/1998 by SB)

Questions? sburke@hep.ucsb.edu