mvc t *> >?)a C-tto? ^ MDDC - 1108 UNITED STATES ATOMIC ENERGY COMMISSION VOLTAGE SUPPLIES FOR THE MASS SPECTROGRAPH by Wilfrid Rail 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. DEPOSITORY Technical Information Division, Oak Ridge Directed Operations AEC, Oak Ridge, Tenn., 10-1-48-1500 Printed in U.S.A. PRICE 5 CENTS 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 0.5 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 megohm 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 full scale. * 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. MDDC - 1108 [ 1 2] MDDC - 1108 GE KENOTRON ACCELERATING HIGH VOLTAGE SUPPLY 35 PEAK KV 10 MA CONTINENTAL X-RAY CORP CHICAGO R, 100.000 OHMS- 200 WATTS - OHMITE CERAMIC SURSE RESISTOR «2 SIX 5. 10 OHM TAYLOR HIGH VOLTAGE TYPE, SMALLCROSS RESISTORS Ci 5^10 - 37500 DC VOLTS MAX OIL FILLED TYPE TR-I 500 VA 435 SOLA CONSTANT VOLTAGE TRANSFORMER CAT NO 30808 Figure 1. Accelerating voltage supply for mass spectrograph. TR-I NON SATURATING REACTOR AIR-GAP ADJUSTED TO MAKE V*V SECONDARY TAPS ADJUSTED FOR BEST REGULATION TR2 SATURATING REACTOR TR3 HIGH VOLTAGE TRANSFORMER Rl IOOK 2W R2 lm«g 2W BOSTON TRANSFORMER CO, CAMBRIDGE , MASS R3 CI C2 2 5 M-20WIIO-250K I^F- 5000 V 2^F-2000 V 2W EACHI C3 IfF- 2500V Figure 2. 5000 volt regulated power supply. Iiilipi 3 1262 08907 9791