''^.M V.S'^ii:)j:)c.-^3v V f MDDC - 834 UNITED STATES ATOMIC ENERGY COMMISSION THE TECHNICAL ASSOCIATES SCALER by Ernest Wakefield U.ij. UtHUiii lOh'i This document consists of 5 pages. Date of Manuscript: May 2, 1944 Date Declassified: March 9, 1947 This document is issued for official use. Its issuance does not constitute authority to declassify copies or versions of the same or similar content and title and by the same author(s). Technical Information Division, Oak Ridge Directed Operations Oak Ridge, Tenr >ssee THE TECHNICAL ASSOCIATES SCALER By Ernest Wakefield INTRODUCTION The Technical Associates Scaler with a scale oi i28 is a Columbia-type scaler with a potentiome- ter in the scaling stage plate circuit. Interstage coupling is the conventional variable air capacitance. Its method of operation and its circuit diagram, together with its components, are described solely for informational purposes. PHYSICAL DESCRIPTION The Scaler One of these scalers, complete with cables shield, and G-M tube, was ordered for observational purposes on December 9, 1943 and received March 3, 1944. The scaler is of double cabinet style, standing almost twice as high as the Offner scaler. Reference to the attached drawing showing chokes, together with realization of the double height, makes this unit nearly twice as heavy as the Offner scaler. Mountings of scaler parameters are on small plasUc boards, one for each stage. All the connecting wiring is black in color, is not harness-wired, and is in a black chassis; hence servic- ing is not easy. A neon lamp is provided for each of the tubes in the seven stages. Shield, G-M Tube and Recorder The lead shield, finished in a crackle gray, has quite a professional appearance. The lead is but 1 5/32 inches in thickness, giving a relatively lightweight shield. For comparison purposes, the lead on a standard Columbia Metallurgical Laboratory shield is 1 1/2 inches, with a brass inner liner of 1/8 inch. Mounting of the G-M tube is from two brass rods supporting a BakeUte holder. The tube is of the Eck and Krebs type, which, unfortunately, was broken in shipment. As the scaler operates on a posi- tive pulse, the outer electrode is not grounded but brought to the grid of the input tube. A Cenco impulse -type recorder is furnished. As is known, the external appearance of this is similar to the Cyclotron Specialties recorder. This Cenco recorder failed the second day of operation. ELECTRICAL DESCRIPTION Scaling Action Due to the relative sizes of CIO and Cll, pushing the reset switch places a negative charge on the control grid of VI, causing the plate to rise and the neon light to conduct and light. The screen in V2, connected to the plate of VI, is high in potential, and current flows in this circuit. As a result, the plate of V2 is at a low potential; hence, all the lower neoi lights ai-e extinguished. A positive pulse arriving from the G-M tube causes V8 to conduct curr nt, lowering the potential on the plate, which places a negative pulse on the suppressor grid of both VI and V2. This momentarily reduces the MDDC - 834 H I 2 MDDC - 834 current in V2, making the plate more positive. As the screen of VI is connected to this plate, a rise in the screen potential of VI causes VI to conduct, because the cathode of VI is not as positive as the cathode of V2, because of the memory condenser. This lowers the plate potential of VI. As the screen of V2 is connected to the plate of VI, this further cuts off V2, so that the lower neon lamp has now lighted. VI is now conducting. The next negative pulse arriving from V6 depresses the suppressor grid potential of both VI and V2, but succeeds in decreasing the current flow in VI. The plate of this tube becomes more positive, which transmits tins increa.se in potential to the screen grid of V2, and memory condenser action causes V2 to conduct current. The plate of V2 drops in potential, which further cuts off VI and trans- mits through C2 a negative pulse, which acts on the next stage as just outlined. Hence, for every two negative pulses only one has passed through the stage. Output Circuit S2 is a selector switch, which permits this scaling circuit to be a scale of 2, 4, 8, 16, 32, 64, and 128. As an example, the second negative pulse arriving at the input to the first stage cuts off VI and causes V2 to conduct. This action increases the plate potential of VI. This increase in potential, which with successive pulses gives a square wave output from a stage, is carried through switch S2 and sharpened into a pulse by the differentiator circuit C4 and R 13. This differentiated square wave is applied to the control grid of V3 (a 6S.T7) , which acts as a buffer for the multivibrators V4 and V5. With V5 alternately conducting, a square wave appears at the plate to operate the recorder. Regulation of the High-Voltage Supply This circuit is almost identical with the Offner and Higinbotham circuits as described in these reports. At the risk of recapitulation, the action is as follows: One side of the high-voltage trans- former is grounded while the other is connected to the plate of a 2x2 half -wave rectifier, the cathode of which is connected to the plate of V7 (an 809), which acts as a variable resistance in the circuit. The cathode of this is the high voltage supply. The control grid of the 809 is in turn controlled by V8 (a 6C6). Suppose the high voltage increases. More current flows through the bleeder resistances, which causes the grid to rise in potential with respect to the V12 (a VR105) controlled cathode. This increases the conduction of V8, lowering the potential of its plate, which in turn lowers the grid of V7, which effectively increases the resistance in the high-voltage supply. This allows less current to reach the bleeder resistances, and the control grid of V8 returns to its earlier potential. C12 is connected between the high-voltage output and the control grid of V8 and minimizes transients and ripple, similarly to the method just described. Low -Voltage Supply The low-voltage supply is conventional, with perhaps greater attention placed on regulation than is normal. MDDC - 834 3] W---<^ 00 o a> 1—1 CO u to u 0) o u bO bO [ 4 MDDC - 834 GEIGER COUNTER, SCALE OF 128 (as furnished by manufacturer), Referring to Figure 1. Condensers Tubes CI 0.1 fxf 600 V Paper C2 10-70 fifif Air Trimmer C3 0.1 /if 600 V Paper C4 10-70 tini Air Trimmer C5 50 utif Mica C6 0.05 fif 600 V Paper C7 0.1 iii 600 V Paper C8 0.1 /if 600 V Paper C9 2. Mf 200 V Paper CIO 0.03 /xf 400 V Paper Cll 0.005 iii 400 V Paper C12 1/if 2000 V Oil C13 1 /if 3000 V Oil C14 8 /if 600 V Oil C15 8 /if 600 V Oil C16 8 /if 600 V Oil C17 8 /if 600 V Oil Misc ellaneous VI 6SJ7 V2 eSJ7 V3 6SJ7 V4 6SJ7 V5 6F6 V6 6SJ7 V7 809 V8 6C6 V9 2x2/879 VIO 5Z4 VI 1 VR105 V12 VR105 V13 VR105 Tl 6.3 V 2.5 amp 6000 v Insulation T2 2.5 V 1.75 amp 6000 v Insulation T3 6.3 V 1 amp 2000 v Insulation T4 2000 V 5 ma 6000 v Insulation T5 Power Transformer Thordarson: T-17R30; 370-0-370 280 ma; 5. v 3 amp ; 6.3 v 7 amp CHI Filter Choke, Thordarson T67C49 12 henrys 200 ma 80 ohms CH2 Filter Choke, Thordarson T16C07 32 henrys 85 ma 375 ohms CH3 Filter Choke, Thordarson T16C07 32 henrys 85 ma 375 ohms CH4 Filter Choke, Thordarson T16C07 33 henrys 85 ma 375 ohms Ml 0-1 DC Milliammeter 51 SPST Toggle Switch; on front panel, engraved "COUNT" above switch 52 U-Point Selector Switch Mallory 1315L, on front panel, engraved "SCALE 2, 4, 8, 16, 32, 64" 53 Push Button Switch Mallory 2003 or Utah 666, on front panel, engraved, "RESET" 54 SPST Toggle Switch, on front panel, engraved "HIGH VOLTAGE" above and "OFF" below 55 SPST Toggle Switch, on front panel, engraved "ON" above and "OFF" below CUl Amphenol 04 Chassis Unit, rebuilt as single contact, using GR Plug , on lead shield CCl Amphenol 04 Cable Connector, rebuilt as single contact, using GR Jack CU2 Amphenol 04 Chassis Unit, rebuilt as single contact, using GR Jack , on back panel, en- graved "COUNTER HV" CC2 Amphenol 04 Cable Connector, rebuilt as single contact, using GR Plug CU3 Amphenol 80C1 Chassis Unit, on lead shield CC3 Amphenol 80F1 Cable Connector CU4 Amphenol 80C Chassis Unit, on back panel, "COUNTER SIGNAL" CC4 Amphenol 80M Cable Connector CU5 Amphenol PC2F Chassis Unit, on back panel, engraved "EXTERNAL ON-OFF" CUB Amphenol PC3F Chassis Unit, on back panel, engraved "REGISTER" CU6 Amphenol MC3M Cable Connector used for connecting register CUB Amphenol MC2M Cable Connector used for connecting external timer CUB CC3 and CC4 require 7030 spring for use with Amphenol 76-22S Coaxial Cable Jl Banana Jack, on front panel, engraved "1" J2 Banana Jack, on front panel, engraved "2" MDDC - 834 X3 Banana Jack, on front panel, engraved "3" J4 Banana Jack, on front panel, engraved "4" LI Line Switch Indicator Lamp L2 High-Voltage Indicator Lamp Rl 0.1 megohm IRC Type BT-1/2 R2 800 ohm IRC Type BT-l/2 R3 500 ohm IRC Type BT-1/2 R4 800 ohm IRC Type BT-1/2 R5 1 megohm IRC Type BT-1/2 R6 1 megohm IRC Type BT-1/2 R7 0.5 megohm IRC Type BT-1/2 R8 50,000 ohm IRC Type BT-1 R9 50,000 ohm IRC Type BT-1 RIO 25,000 ohm WW Clarostat Rll 50,000 ohm IRC Type BT-1 R12 50,000 ohm IRC Type BT-1 R13 0.5 megohm IRC Type BT-1/2 R14 10,000 ohm IRC Type BT-1 R15 0.1 megohm IRC Type BT-1 R16 1. megohm IRC Type BT-1 R17 0.1 megohm IRC Type BT-1 R18 0.1 megohm IRC Type BT-1/2 R19 12,000 ohm IRC Type BT-1 R20 25,000 ohm WW Clarostat, on chassis, engraved "REGISTER ADJUST." R21 50,000 ohm IRC Type BT-1/2 R22 0.1 megohm IRC Type 3T-1/2 R23 750 ohm IRC Type BT-1/2 R24 25,000 ohm IRC Type BT-1 R25 ' 0.1 megohm IRC Type BT-1 R26 15,000 ohm IRC Type DHA R27 0.1 megohm IRC Type BT-1/2 R28 0.1 megohm IRC Type BT-1/2 R29 0.5 megohm IRC Type BT-1/2 R30 2. megohm IRC Type BT-1/2 (mounted close to counter tube) R31 0.5 megohm Potentiometer, on chassis, engraved "INPUT ATTENUATOR' IRC Type DS 11-133 R32 1,000 ohm WW Clarostat, on chassis, engraved "AMPLIFIER BIAS." R33 10,000 ohm IRC Type AB R34 15,000 ohm IRC Type AB R35 0.25 megohm IRC Type BT-1 R36 0.1 megohm IRC Type BT-2 R37 1.7 megohm (Bank of three 0.5-meg and one 0.2-meg; all BT - 2) R38 0.2 megohm Potentiometer GR Type 471, On front panel, engraved "HIGH VOLTAGE CONTROL." R39 0.1 megohm IRC Type BT-2 R40 2. megohm IRC Type BT-2 R41 10. megohm (Sank of five 2-meg IRC Type BT-2) R42 1.000 ohm IRC Type BW-1 R43 1,000 ohm IRC Type BW-1 R44 6,000 ohm IRC Type ABA R45 6,000 ohm IRC Type ABA UNIVERSITY OF FLORIDA ■lilllllllllllllllllllllll 3 1262 08910 9432 1