A High Voltage System with 60 High Voltage

A High Voltage System with 60 High Voltage Power Supply Channels in 2 U Height EURO Crate Masatosi IMORI, Nagataka Matsui, Masaya ISHINO, Toshiyuki Kimura 1, Tomoharu Mieno 1, Satoru Imada 1 and Masafumi Katsuno 2 International Center for Elementary Particle Physics, University of Tokyo 7 -3 -1 Hongo, Bunkyo-ku, Tokyo 113 -0033, Japan 1 NF 2 NEC Corporation, 6 -3 -20 Tsunashima Higashi, Kohoku-ku, Yokohama-shi 223 -8508, Japan TOKIN Corporation, 7 -1, Kohriyama 6 -chome, Taihaku-ku, Sendai-shi, 982 -8510, Japan

The High Voltage System • 60 independent channels of HV power supply are housed in 2 U x 19’’ EURO crate x 50 cm in depth – Each board contains 3 ch. of HV power supply – The system consists of 20 HV boards & a control board • A ceramic transformer generates high voltage

generation of HV by Ceramic Transformer (CT) • HV is generated by piezoceramic effect – CT is made of ceramic bar – CT contains no magnetic material operational under magnetic field • • • rating resonance frequency input voltage efficiency amplitude ratio output voltage 5 W ~ 150 k. Hz > 6 V 95 % > 120 > 707 V

amplitude ratio vs driving frequency • carrier wave is supplied to CT and it’s amplified by internal resonance circuit of CT ~ 150 k. Hz • The amplitude ratio is a function of the driving frequency of carrier wave control HV = control frequency of carrier wave

The High Voltage System • output capability – each channel supplies stabilized HV up to 4 k. V to load more than 20 Mega ohm ( ~200 micro-Amp. ) • magnetic field tolerance – we confirmed it’s operational under the magnetic field of 1 -Tesla • Radiation Hardness – 60 Me. V protons ; 1 E 11 (~14 krad) [tested at PIF @ PSI ] – Cobalt-60 gamma-ray ; ~300 krad the system cope with both conditions

The High Voltage System (cont’d)

HV control and monitoring system • The HV power supply is controlled by external computer via USB interface (chosen for general purpose application) – GUI based software for Windows OS – CUI based software for Linux OS are developed • as a basic functionality – individual channel can be turned on and off – output voltage can be set – output current can be monitored

current monitoring system & chamber spark • Each HV board has 9 bit A/D converter (CS 5523) – output current is monitored with a sampling rate of 80 Hz (12. 5 msec) • there are two operation modes mode full scale precision maintenance 10 micro A 20 n. A operation 250 micro A 500 n. A leak current monitoring for chamber conditioning working mode under particle flux • This sampling rate and resolution of current monitor allows us to detect “spark” happened in chamber because of neutron. current 10 micro Amp 100 msec time

over current shutdown • more over, basic functionality like – turns off power supply, if output current keeps larger than a setting threshold during a prescribed time interval (Dt = 0. 1 msec) is implemented • This process is implemented in FPGA (anti-fuse type , mounted on each HV board) by hard-wired logic. – no software is necessary • The system can be operated safely and can be applied to a delicate object like wire chamber, … etc

output current and return current • The output current is measured by the return current • The voltage caused by the return current across the sense resister is amplified and digitized by A/D converter.

next revision in progress • Four terminal ceramic transformer – Tokin Corp. develops four terminal ceramic transformer dedicated to the high voltage power supply A

3 terminal ceramic transformer ~ sharing the common Ground CT shares common ground between primary and secondary A because of this loop current, the current measured at B is not always the one at A with using 4 -terminal CT, ground can be isolated, and the current measurement can be done more precisely

summary • The HV power supply of 60 channels housed in 2 U x 19’’ x 50 cm is fabricated • Ceramic transformer is used for generating HV – magnetic field tolerant (1 Tesla) • Radiation hardness – 60 Me. V protons ; 1 E 11 (~14 krad) – Cobalt-60 gamma-ray ; ~300 krad • output current monitoring – important for the operation of delicate object like wire chamber – current monitoring with a frequency of 80 Hz • for the detection of the chamber spark signal • next version is in progress – four terminal Ceramic Transformer will be used to improve output current monitoring

Elimination of 3. 5 V • So far the ceramic transformer employed in the power supply is driven by the driver circuit which is powered by 3. 5 V. • The dedicated transformer is driven by the driver circuit powered by 48 V. • The high voltage power supply employing the dedicated transformer eliminates the power supply of 3. 5 V, which simplifies supply voltages to +/- 5 V and 48 V.

Stabilization of Output Voltage