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UNITED STATES ATOMIC ENERGY COMMISSION
VOLTAGE SUPPLIES FOR THE MASS SPECTROGRAPH
A. E. Shaw
Argonne National Laboratory
This document consists of 2 pages.
Date of Manuscript: June 25, 1946
Date Declassified: July 7, 1947
Its issuance does not constitute authority
for declassification of classified copies
of the same or similar content and title
and by the same authors.
`-)U C OF L IOR
Technical Information Division, Oak Ridge Directed Operations
AEC, Oak Ridge, Tenn., 10-1-48-1500
Printed in U.S.A.
PRICE 5 CENTS
. 1 .9 :
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VOLTAGE SUPPLIES FOR THE MASS SPECTROGRAPH
By Wilfrid Rail and A. E. Shaw
Two DC voltage supplies are needed for the double focussing mass spectrograph, an accelerating
voltage of up to 30,000 volts and a deflecting voltage of up to 3500 volts.
A very convenient 35 kv high voltage supply made to order by the Continental X-Ray Corporation
of Chicago, is illustrated in Figure 1. It is mounted in oil in a welded steel case. The 35 kv trans-
former is rated at 10 ma and was tested at 25% overvoltage. The secondary is 26.000 ohms and will
stand shorting. Neither end is grounded and the mounting will stand 80 kv. Placing the condenser a-
cross the output caused electrical break-down in the bakelite mounting brackets and Mykroy had to be
used. The special 8.5 volt, 14 amp filament transformer is insulated from the high voltage transformer.
The rectifier is a KR-6, GE-X-Ray Kenotron.
The input of the high voltage transformer is controlled by means of a type 200-CU Variac whose
input is stabilized by a 500 VA, 4.35 amp Sola Constant Voltage transformer. The output is smoothed
by a 0.6 microfarad oil-filled condenser rated at 37,500 volts DC. and a surge resistor of 100,000 ohms
at 200 watts. The voltage is measured on a 0-1 milliammeter in series with 30 megohms supplied by
six 5 megohm Taylor High Voltage Type Shallcross resistors. A 50 megohmn 100 watt, type MVR, IRC
High Voltage resistor has also been found satisfactory.
The small AC ripple need not be removed because much larger fluctuations are superimposed
upon the accelerating voltage by the high frequency spark circuit. The position of a line on the photo-
graphic plate is determined by the electrostatic deflecting voltage and the magnetic field. The require-
ment on the accelerating voltage is only that the energy range of ions produced include the ions which
will pass into the 90* condenser without being deflected too much or too little to get through.
A convenient deflecting voltage supply with regulation adequate for ordinary analytical work has
been designed by the Instrument Section of the Metallurgical Laboratory. The regulation of this supply
is achieved by means of a special saturating reactor and is good to between 1 part in 500 to 1 part in
1000. The output is filtered by a Pi filter as shown. Neither side of the output was grounded since better
focus is obtained when the ground potential surface in the condenser is near the middle. It was found
worth while to run a series of tests to determine the best point of the dropping resistor to be grounded.
The voltage was read on a 0-1 milliammeter which could be connected to read either 2500 or 5000 volts
The resolution of a double focussing mass spectrograph depends on the regulation of the deflecting
voltage supply. When optimum resolution is desired for careful mass measurement, it was found advan-
tageous to replace this supply with a less convenient but more stable set of 45 volt Mini-max batteries
in series. Visibly sharper lines were obtained.
Several electronically regulated supplies have been tried but found to be troublesome because of
RF pick-up. Recently the Instrument Section constructed a 3500 volt supply in which most of this has
been filtered out, but it has not yet been tested enough to be compared with the supply described above.
However, the saturating reactor regulator has been found very satisfactory for ordinary analytical work.
..154 wOLIAGF SUPPLY
35 PEAT KV 10 MA
CONTINENTAL X-RAY CORP
11 10.OOO OM5.200 WATTS-OHMITE CERAMIC SURE
R SIXA Sait OHM TAYLOR HIGH CLTAGE TYPE,
C, ) Bpfd 37500 DC VILTS MAX OIL FILLED TYPE
IH 500Vl 435 SOLAR CONSTANT VOLTAGE
TRANSFORMER CAT NO 3080B
Figure 1. Accelerating voltage supply for mass spectrograph.
TR I NOTi SATURATING REACTQOR
AiR-GAiP ADJUSTED TO MAIL a 1
SECONDARV TAPS ADJUSTED FOR I BOSTON TRANSFORMER CO,
BEST RECULATIHON CAleRIDGL, MASS
TR2 SATURATING REACTOR
TR3 HIGH VOLTAGE TRANSFORMER
RI IOOK 2W
RE Iw W 20
R I 5 M-20Wi0-250K. 2* EACHj
CI iFf- 5000 V
Figure 2. 5000 volt regulated power supply.
UNIVERSnrY OF FLORIDA
3 1262 08907 9791
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