yi.fitTf/ ^«:^^3. WCliy^T^^ JllntS 4^ MDDC - 832 UNITED STATES ATOMIC ENERGY COMMISSION PRELIMINARY REPORT ON THE HIGINBOTHAM SCALER by Ernest Wakefield Argonne National Laboratory U_ 'J- S. DEPOSITOR r Date of Manuscript: Date Declassified: April 26, 1944 March 9, 1947 Issuance of this document does not constitute authority for declassification of classified copies of the same or similar content and title and by the same author. Technical Information Branch, Oak Ridge, Tennessee AEC, Oak Ridge, Tenn., 5-20-49--850-A4931 Printed in U.S.A. PRICE 5 CENTS PRELIMINARY REPORT ON THE HIGINBOTHAM SCALER By Ernest Wakefield SUMMARY Because of the interest in the Higinbotham scaler, its operation is described and some test data is presented together with the circuit diagram. A typical parts list is included. This circuit, particularly the input, is subject to change as experience is gained. Tests indicate that the circuit parameters of a Higinbotham circuit are wide. This conclusion is based on tests of two scalers made by Wendell Bradley's group and tested largely through the efforts of Stanley Cooper. Further work is envisaged and will be reported on in due course. John Simpson reports that a Higinbotham has been driven at 800 K.C. He achieved this with a spe- cial input circuit and a regular pulse. In the early stages he was also careful about stray capacitances. An oscilloscope was used as a recorder. CIRCUIT OPERATION Description of Scaling Action in the Higinbotham Circuit The reset button being pressed places a positive potential on the right hand grid of each 6SN7 (as shown in the diagram). This causes all the right hand triodes to conduct, hence lowering their plate potentials. This cuts off the left triode and also depresses the potential on the left plate of the preced- ing connecting diode. The scaler is now ready to receive pulses. A negative pulse being applied to the input trigger pair causes the first plate to go positive. This pulse is transferred to the grid of the second tube of the trigger pair causing this latter plate to go neg- ative. As the left plate of the diode is at a lower potential than the right, the latter conducts with this negative pulse. This drops the potential of the diode plate and a negative pulse is transmitted to the grid of the triode which has been conducting current. This action decreases the current flow through this tub? causing its plate to become more positive, which transmits a positive pulse to the grid of the paired triode. The plate of this triode drops in potential, which lowers the plate potential of the pre- ceding diode, which has just conducted. This action also lowers the grid potential of the triode pair which had just decreased its passage of current further cutting off this tube. It can be seen that a positive pulse is transmitted to the next diode stage, but has no effect since it decreases the plate- cathode potential which is already too low for the diode to conduct. The ne.rt negative pulse out of the input circuit causes the left diode to fire, because its plate poten- tial is higher than the adjoining one. This transmits a negative pulse to the grid of the left triode which is carrying current, decreasing this flow. The plate, rising in potential, puts a positive pulse on the grid of the adajacent triode which conducts. The plate, dropping in potential as a result, places a negative pulse on the cathode of the following diode. Hence, for two negative pulses applied to the scaling stage only one has gone on. MDDC - 832 1 MDDC-832 I vV\A/- —^ ^/V\A4vW■ I AA/V — 8 > > > _o " ; 5 : i; c; ' >• o in J-- '- " £ 2 3 2: CO «5 ;; -; Jo «o «= > > i < t- to — — « M CO VyVAi -^\AAA-' 'VVN^ ^AAA^Ill HHII" I MDDC - 832 The appliance of two negative pulses to the last stage causes a positive pulse to be emitted. This places a firing voltage across the neon coupling lamp, which now passes current. This increases the potential across R66 which makes the grid of the output tube, a 6V6, more positive. This tube becomes conducting and draws current through the recorder. To decrease the reluctance of the magnetic circuit (in the Wizard recorder) iron arms rotate operating a pawl and gear registering a count. To reduce the back voltage and hasten operation of the recorder a 200,000 ohm resistor in parallel with a .06 mfd, 600 volt condenser is placed in parallel with the recorder. The low voltage supply is conventional. Operation of the Regulated High Voltage Supply One end of the secondary of the high voltage transformer is grounded and the other is connected to the plate of a 2x2 half -wave rectifier tube. The cathode of this, which is at a potential of about 1600 volts, is connected to the plate of an 809 triode, which is also connected to a 2 mfd filter condenser to ground. The 809 acts as a variable resistance in the high voltage circuit and is controlled by the 6SJ7 in the manner given in the next paragraph. Suppose the high voltage at the cathode of the 809 becomes too high. More current then passes through the bleeder resistances R67, R68, R69 and R70 to ground. From potentiometer R68 the control grid of the 6SJ7 becomes more positive with respect to the cathode permitting more current to pass through this tube. This lowers the potential on the plate of the 6SJ7, which in turn lowers the grid poten- tial on the 809. As this effectively increases the resistance of the 809, less current is supplied to the high voltage supply and hence the voltage decreases. A decrease in voltage gives the opposite effect. 809 RF POWER AMPLIFIER P GRID 3/ ^2NC H4^ ^1H TOP VIEW 2X2/879 HALF WAVE HIGH VACUUM RECTIFIER NC2/- --vSNC H 1 4HaK 6SN7 TWIN TRIODE AMPLIFIER Gt, 4^ ^5 Pt, Kt2 3 Go 1 6 Kt, 7H 8 H SHELL 1 6V6BEAM POWER AMPLIFIER °2 1- — ^5e, P 3/ \6 H 2\ 77 H SHELL 1 8 K 3SJ7 TRIPLE-GRID DETECTOR AMPLIFIER G,4, 5K G3 7 Xe G2 H \ jlH SHELL 1~ — "a p Figure 2. Several of the tubes in the Higinbotham scaler. MDDC - 832 o o o (_J o o a. a. o^ o o o^ lf> o^ o^ o o d" o in CQ oo CO o « «NJ m o '-* o o ° — CO CO 00 O. x: w CM a. x: O O O O I I o o o o o o 05 '-t »-< t- 05 CO o o o o o o o o *" 00 o o o a. a a a o o o o o irT a a a a o ■a pq '-^ > ■a E E a X! s s s in a a t jz js ^ O o j= o o bo a> o o o o 01 ,^ e a s o o o o o o o^ o_ o d" lo" o ^ o o « in I— 1 >— < o • r-l O - ^ ^ in CO -^ in u H s lslll W (Q ^ '•-1 uu t! " CO '" -S P T3 ^ jb -e s ! » -s I y " « QJ tH q; ^ M 0] 0) ^ •■§ B s -a •§ _ 3 m h " I I. s ^ « ^f ° I a o ^ rt O S " 2 « E g .5 H MDDC - 832 PARTS LIST V14 2x2/879 VI 5 809 VI 6 68 J7 V17 5Y3GT V18 6V6 LI Stop Count Indicator Lamp, 6v L2 Power Supply Indicator Lamp, 6v L3 High Voltage Supply Indicator Lamp, 6v Rl 1 megohm, 2 watts R2 1 megohm, 2 watts R3 2 megohms, 0.5 watt R4 0.1 megohm, 1 watt R5 24,000 ohms, 1 watt R5A 5,000 ohms, 1 watt R6 3,300 ohms, 1 watt R7 5,000 ohms, 4 watts wire-wound potentiometer R8 1,000 ohms, 1 watt R9 15,000 ohms, 10 watts RIO 0.1 megohm, 1 watt Rll 1 megohm, 0.5 watt R12 0.2 megohm, 1 watt R13 0.1 megohm, 1 watt R14 20,000 ohms, 2 watts R15 5,000 ohms, 1 watt R16 15,000 ohms, 2 watts R17 10,000 ohms, 3 watts R18 0.2 megohm, 1 watt R19 0.1 megohm, 1 watt R65 1 megohm, 0.5 watt R66 0.5 megohm, 0.5 watt R71 5 megohms, 2 watts R72 50,000 ohms R74 30,000 ohms R 75 200,000 ohms, 2 watts R76 5,000 ohms, 20 watts R77 5,000 ohms, 20 watts R78 2,000 ohms, 10 watts CI 75 tJLui, 5,000 volts C2 ,05 Mf,. 2,000 volts C3 50 M/if C4 10 Mf C5 50 inii C6 0.01 Mf C7 50 Ml^f C25 .06 Mf, 600 volts DC C26 20 Mf, 450 volts DC 027 20 Mf, 450 volts DC This is not a complete list of the resistors and capacitors used in this unit. However, the values here given for the first scaling stage are typical of all six scaling stages. END OF DOCUMENT UNIVERSITY OF FLORIDA 3 1262 08910 9739