Maintenance experience and development on the "California" scaler

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Material Information

Title:
Maintenance experience and development on the "California" scaler
Series Title:
United States. Atomic Energy Commission. MDDC ;
Physical Description:
6 p. : ill. ; 27 cm.
Language:
English
Creator:
Elmendorf, W. T. E
U.S. Atomic Energy Commission
Publisher:
Technical Information Division, Oak Ridge Operations
Place of Publication:
Oak Ridge, Tenn
Publication Date:

Subjects

Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

Bibliography:
Includes bibliography references.
Statement of Responsibility:
by W.T.E. Elmendorf.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 005023490
oclc - 277228034
System ID:
AA00008531:00001

Full Text
3flrt 7Th'/


UNITED STATES
ATOMIC ENERGY COMMISSION

OAK RIDGE.

TENNESSEE


MAINTENANCE EXPERIENCE AND DEVELOPMENT


ON THE


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"CALIFORNIA


W. T. E


SCALER


Elmendorf


or use within the Atomic Energy Commis


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nical Information Division, Atomic Energy Commission,


for additional copies


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MDDC


- 996


MAINTENANCE EXPERIENCE AND DEVELOPMENT


ON THE


"CALIFORNIA


SCALER


ByW


Elmendorf


INTRODUCTION


..The writer has


been working with


29',,1943, and has been maintaining the
'205"Aince that time. This report is desi
Us.;;/ : "
. tlie operation of the California Circuits,
W. rrifteahd members of Mr. English's g


G. English's


group in building 706-A since November


California Circuits in the counting room of building


gned to give a genera
and report on some
roup have carried on.


I discussion of the operation of
experimental work that. the
Maintenance data is for the


:. period from 11
: *' ; iI


9/43 to 1/15/44.


CIRCUITS IN USE


The California circuits in Building 205 are composed of three


type A Beta circuits


: drawing 717-B-
..p.:tyi Alpha ci
.4...p.gnetic
V alpha-sets.
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12) using N
rcuits (Dtvg


eher-Harper quenching for mica window G-M tubes and five


717-B-13) with type A amplifiers


(Dwg.


type alpha chambers and two standard alpha chambers


is checked with a
are entered in th


717-B-


There are


used with the five


standard every shift and adjustment made if necessary.
e set log book and these complete records are available


DETAILED DESCRIPTION


r CIRCUIT (717-B-12)

consistss of an external Neher


ter amplifier


-Harper quench tube (6J7G),


a 6SJ7 amplifier


No maintenance of any kind has been performed on this cir-


)/43 except for replacing G-M tubes,
d their windows broken.


four of which lost their plateau and


Experimental attempts to build the Neher-Harper tube into the set have failed to date
as the pulses obtained without modification of the input amplifier would not trip the scaler.
Work on this phase will be continued.
'm :
. 'Examination of the relative plateaus of an Eck Krebs G-M tube with resistance and Neher-


. Harper quenching was made.


The res


ults obtained are included in Table 1 and show that


Sthe plateau was lengthened by a factor of between 2 and 3 by use of Neher-Harper quenching.


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MDDC


- 996


The difference in counts per minute shiownn thed ablle was dfe largif tb different geome-


try of the,


source.


However,


the writer understands that thie resolution of the Neher-Harper


circuit is slightly less than that of a resistar


The circuit used in the Type A Scaler (717


quenching without a preamplifier.
to give a pulse of the proper sign,


ice quenched circuit. "

-B-12) is unsuitable for use with resistance


A circuit consisting of two amplifier tubes is req


large enough totrip the sealer.


come in the experimental Beta Set (717-B-11) by using an input circuit


very


similar to the


Chicago Type,


replacing the second 6C5 wit a 6SJ7;


B. ALPHA CHAMBERS (DWg.


t


717-B14)


The electronic circuits of the magnet and standard alpha chambers are the same.


teries


Bat-


supply all voltages used.


Operating experience with these chambers has been rather unsatisfactory


It has been


necessary to replace the 38 tube at frequent iliterval. The criterion for replacement of


the tube is high hash level or low counting rate on the standard


sample.


it>


ALPHA AMPLIFIER (Dwg. 717-B-14)


This amplifier is a three tube non-linear nohi-fed back amp


lifier us


ing a D.


C. filament


supply for the first tube.


The first and last tube are zero bias tubes and the gain control


is normally set so that the alpha pulses saturate the last tube.


4x*:


As"would be expected from the design, the a lttiml# is


extremely critical


as to the tribes,


the first 6J7 being the most critical.
ating trouble has been experienced.


However, when tubes


have been selected


, little oper-


Only one 6J7 has been replaced in 205 building since


December 1.

The gain plateau is usually quite long, varying from the point where the alpha pulses


first saturate


, to the point where the hash counts.


Thd Very good signal to no


ise ratio en-


ables alphas to be counted over 5 x 106betas in a standard chamber


at 8% geometry>with a magnet chamber.


and over 10a betas


>""


The feature: of saturating the outgpt tul e enable


sf the control chemists to judge very well


as to whether a sample can be counted.


The gain can be reduced only so far as


will still


give saturated pulses and, if the hash is near the tripping height then,


the sample cannot


be codtted reliably. This enables an inexpbriencea operator to judge when he is getting
near the danger point" the picture is very elat othe oscillograph.


Critical circuit constants in this circuit are the


condenser and the screen dropping


resistdrs


4311PP


a<


This difficulty was over-


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MDDC


HUNTOON


- 996


STROHMEYER PULSE SHARPENER (717-B-13)


This is a multivibrator


circuit which serves


to provide


sharp, even height pulses


to the


scaler


Operating difficulties


have been confined to defective 6B8 tubes


two tubes


having


been replaced


December 1


A tube tester will not give a re


liable


indication as


whether a tube is good for this


service.


SE.: TRIODE SCALING STAGES (Dwg.


717-B-11


, 12, and 13)


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e triode


1C5 tubes


scaling


stages


consist of a 6C5


with their grids cros


proven to be very reliable and ea


e scaling stages


of these


s coupled


sy to


se


interstate amplifier biased beyo
to the plates of the opposite tube
rvice, only five service calls du'


r V


being encountered between November


were due to bad mica


:reset switch, or
e scaling stages
tive rectifier tu


condensers


nd cutoff and
. This circuit
e to failure to


, 1943 and January 13, 1944.


(bad on a condenser tester), one due to an


ne due to a shorted 6C5, and one due to defective 400,000 ohm resistors
. Since January 13, two failures have been encountered, both due to
bes. The characteristic of this failure is the same as that due to low


,e- the interstate amplifiers' fail to pass the


onstants were such that


itbllta


pulse


On one


the B+ with good rectifier tubes


ges on 12 operating sets were taken on January 1


Range of B+ voltage 330


was


it, it was found that the
barely high enough.


with the following


results:


- 390 volts.


Range of interstate amplifier B- voltage


!.-ra e of


scaling pair grid return v


aRahge of conducting plate voltages


dRange of grid voltage


-35 to -40 volts.


oltage -69 to -'
50 to 180 volts.


18 volts


-5.3 to 17.


':Maximum grid difference.


Regular set 9.4 volts.


. i .
Grid voltages taken by removing the scaling pair with all other tubes in.


ds data demonstrates that the scaling


stages are not critical


bound that the following voltages are of use in trouble shooting.


should be


-35 to -40 volts; plate voltage of the conducting tube


as to voltages.


s


The writer


Interstage amplifier
shouldd be under 100 volts.


Gridi tf- the not conducting tube should be at least -35 volts.


should be at least 350 volts.


The stages are not critical


as to tubes and any tube that checks al


right on a tube tester


should .be


failure of a


satisfactory.


6J5;


and BP5 tubes may be used interchangeably.


stage to scale does not necessarily block the set.


set can


However,


scale through


. .and;the 'interpolate meter does not give as good indication of trouble as


the neon lights


used with the Columbia circuit.


The triode scale of 64 (717-B-


11) uses


neon lights for that


reason and because an interpolate meter cannot be used with a scale of 64.
4')
Line voltage stability of the sets is good but the interpolate meters do not read correctly
when the line voltage is different from that at which the calibration potentiometers were


set. The only set that has been thoroughly investigated by the writer for surge stability is


I.


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- 4 -


MDDC


- 996


supply of this
two rectifiers


set differs from that


shown in the drawing imthat two rectifier windings and


were used to get the plus and minus voltages.


OUTPUT STAGE


The output stage uses a 6C5 inverter amplifier and an 884 thyratron to drive
round case recorder. No trouble has been encountered with this circuit to date.
be noted, however, that this output stage will not drive a Wizard Counter.


the Cyclotron


I should


G. HIGH VOLTAGE SUPPLY (717-B-12 and 13)

The high voltage supply uses a single 47 tube to regulate it. It is rather complicated to
stabilize two knobs on the front of the set and a test switch to throw resistance into the
supply to the high voltage transformer being manipulated to give good voltage stabilization.


Practically no load can be drawn from the supply,


the load of a G-M tube and Neher-Harper


circuit counting at a rate of 2000 counts/min. being enough to cause a distinct drop in


voltage.


In addition, the Pyranol output condenser is very critical in alpha service,


conden-


sers good for all normal purposes allowing enough A;


C. ripply to pass through to upset


the alpha amplifier.

Maintenance on this part of the circuits has consisted of replacing defective dropping
resistors in one G-M set and two Pyranol condensers in alpha sets.

One G-M set has been rebuilt to use the high voltage circuit shown in drawing 717-B-16.


This high voltage was stable at 1000 V. outp
load, no meter deflection being, perceptible.


iut from 80 to 135 volts on the variac with no
It was stable in the same way at 1000 volts


when one milliampere was drawn from it at regular line voltage.


No hash was introduced


in the alpha sets by this high voltage and the beta set containing it is now in regular opera-


tion in 205 counting room.
after the initial warm up.


TRIODE SCALE OF 64 (Dwg.


No drift has been encountered in the high voltage of this set


717-B-11)


A triode scale of 64 was builtaccording to the drawing 717-B


-11 except that two rectifier


windings and rectifiers were used for the plus and minus voltage supply.


When first built,


sufficient ventilation was not provided and trouble was experienced with change in the


400,000 ohm dropping resistors.


This trouble has been cured by drilling ventilation holes


in the top of the chassis.


The set was put into operation December 17,


1943 in the 105 Bldg.


counting room. No troubles within the set were. encountered until January 7


1944


at which


time the last two stagesstopped


scaling and the set started to blow fuses.


T


to the 6L6G which had 2 megohms between the grid and ground on fixed bias


'his was traced
. The dropping


resistor network was changed and the set put back into service.with nothing whatever being
done to the scaling stages.


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-5-


MDDC


- 996


Original tune-up of this set demonstrated the necessity for having the


supply adjust-


able so that the


highest conducting plate was below 100 volts


Outside of that


, no unexpected


factors were encountered.


TRIODE SCALE OF 64


- GENERAL REMARKS


The set B+ must supply at least 80 milliamperes and the B-


should


supply 15 ma


use of 6SN7 tubes


instead of 6C5's


for the


scaling pair would reduce the number of


scaling


.tubes required from 18 to-12 and make the layout


comparable to that of a Columbia Type


"Scaler


The B


supply circuit


shown in the drawing provides a circuit that requires only one


rectifier and rectifier winding but requires a VR 90 to prevent the recorder current
upsetting the B minus.


from


If sets like this were manufactured in large quantities, it wou
400,000 ohm resistors plus perhaps 10% 100,000 ohm resistors


precautions need be taken.


Id be advisable to us
. Aside from that no


Use of a bus bar for B+ and B- voltages is


a maintenance viewpoint in that a poor joint to one stage
other stages.


e 10%
special


advantageous from


will not affect the operation of


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Voltage data on the existing
5 volts; B- to amplifiers -3


it pair out,


scale of 64 is as


5 volts.


and the maximum grid to


follows:


B- 410 volts


The grids range from 5
grid difference is 13


to 29 volts


to scaling pair
with tubes of


volts.






MDDC


- 996


PERFORMANCE OF COUNTER G-9

Plateau Runs


VOLTAGE


COUNTS/MIN.


COUNTS/MIN.


RESISTANCE QUENCHING


NEHER-HARPER QUENCHING


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.... ....


Threshold 1928


THRESHOLD


2112


a &.~. .


1000
1040


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2816
2944


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1100
1120
1150
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1200
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1300
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1450
1500


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The lengthening of plateau by means of Neher-Harper quenching is apparent.


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