Design of the high frequency spark source for the mass spectrograph

MISSING IMAGE

Material Information

Title:
Design of the high frequency spark source for the mass spectrograph
Series Title:
United States. Atomic Energy Commission. MDDC ;
Physical Description:
3 p. : ill. ; 27 cm.
Language:
English
Creator:
Rall, Wilfrid
Argonne National Laboratory
U.S. Atomic Energy Commission
Publisher:
Atomic Energy Commission
Place of Publication:
Oak Ridge, Tenn
Publication Date:

Subjects

Subjects / Keywords:
Mass spectrometers   ( lcsh )
Mass spectromtery   ( lcsh )
Electric spark   ( lcsh )
Genre:
federal government publication   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )

Notes

Restriction:
Date Declassified: July 9, 1947
Statement of Responsibility:
Wilfrid Rall.
General Note:
Manhattan District Declassified Code
General Note:
Date of Manuscript: June 17, 1946

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 005023735
oclc - 465277585
System ID:
AA00009315:00001


This item is only available as the following downloads:


Full Text






MDDC 1107



UNITED STATES ATOMIC ENERGY COMMISSION







1i

DESIGN OF THE HIGH FREQUENCY SPARK SOURCE
FOR THE MASS SPECTROGRAPH



by
Wilfrid Rail



Argonne National Laboratory


814GQ IN ,
LIBRA


Manuscript Date:
Date Declassified:


June 17, 1946
July 9, 1947


Its issuance does not constitute authority
for declassification of classified copies
of the same or similar content and title
and by the same author.





Technical Information Division, Oak Ridge Operations
AEC, Oak Ridge, Tenn., 11-15-48--850-11401


Printed in U.S.A.
PRICE 5 CENTS














































*















DESIGN OF THE HIGH FREQUENCY SPARK SOURCE FOR THE MASS SPECTROGRAPH


By Wilfrid Rail


It is the purpose of this paper to discuss the various improvements which have been made in the
design of the high frequency spark ion source.

The circuit, which is quite simple, is shown in Figure 1.

T P S
0 ,

INPUT OUTPUT




Figure 1. Electrical circuits of the frequency spark ion source.

The spark gap, G. breaks down 120 times per second when energized by 3000 to 5000 volts from
transformer, T, whose primary voltage is adjusted by means of a variac. Each time G is closed by
a spark, high frequency oscillations are set up in the tank circuit G, P, C in which the values of P
and C have been adjusted for resonance. These high frequency oscillations are inductively coupled to
a secondary, S, with a 40/1 turn ratio, and placed across the electrodes in the mass-spectrograph.
The early models of the spark circuit, built along the lines of the common laboratory demonstra-
tion tesla spark circuit, were capable of more power output than necessary and were thus bulky and
somewhat inconvenient. The tesla coils, P and S, were 12 inches long with 5 and 8-inch diameters.
Together with a plate glass condenser and the spark gap, these coils were immersed in a five-gallon
earthenware jar filled with oil. The principal reason for the large geometry and oil immersion was
the prevention of high voltage corona and breakdown. Since the spark output is connected to the ac-
celerating voltage of from 10,000 to 30,000 volts, the insulation between P and S must be good. It has
been found that adequate insulation is provided by concentric tubes of Lucite with a 1/4-inch wall.
Use of Lucite tubing and No. 34 Heavy Formex wire in the secondary windings made possible a com-
pact assembly 6 inches long and 2 3/4 inches in diameter.
This assembly consists of four concentric tubes 6 inches long.* The primary of 5 turns is wound
in a groove of 5/16-inch pitch cut in a Lucite rod of 1 1/4-inch OD. This is covered by a blank insu-
lating tube of 1 3/4-inches OD. Over this tube fits the secondary coil of 200 turns wound in a vee-
groove cut 48 threads per inch on a tube of 2 1/4-inch OD, covered by another tube of 2 3/4-inch OD.
The grooves for the secondary windings are cut on a 2 1/16-inch diameter to allow space for a thick
coat of Dow Wax over these windings. The precautions of equal spacing with Lucite thread wall sepa-
rations, of wax coating, and of heavy former insulation on the wire have effectively prevented sparking


*The extruded tubes provided by the manufacturer had to be machined to provide a slip fit.
MDDC 1107 I 1









MDDC 1107


between the various turns of the secondary winding, a difficulty encountered before these precautions
were observed.

The problem of making a positive connection to the secondary windings was solved by the use of
split rings fastened to the Lucite tube at the two ends of the windings. The wire was soldered to these
rings which were tapped to fit binding posts screwed in through clearance holes in the outside cover.
Threading the Lucite was found unsatisfactory. The primary leads pass through holes drilled on the
axis of the Lucite core.

A condenser of fairly small physical dimensions was found to be satisfactory, 2 by 2 1/2 by 3 3/4
inch mica capacitors (Cornell Dubilier Type 86 or Aeroxex Type 1995). The value of the capacity varies
with the other circuit constants in the resonant circuit; we are now using .0044f.
The spark gap used most has been a hydrogen filled (atmospheric pressure) gap consisting of
two 2 mm tungsten electrodes sealed into a Pyrex cylinder with about a 1/4-inch gap between them
(see Figure 2). Experiments have been made with an air gap between tungsten disks. One such gap,




2MM WIRE
30 MM




3-


Figure 2. Spark gap in detail.


shown in CP-2410, Figure 8, consisted of 1/4-inch diameter tungsten disks mounted on larger copper
disks with fins for heat radiation. Gap separation was provided by mica washers. T is operated quite
satisfactorily; however, sputtering from the spark gradually deposited a conducting coat on the mica
surfaces causing a short circuit. This could be corrected by disassembling and scraping the mica.
The hydrogen gap short circuits less often because of the larger glass surface and can be cleaned
quickly by shaking up the carborundum which is sealed in the tube for this purpose. This gap is
mounted in a small oil bath for cooling.

A compact unit consisting of Lucite tesla coils, spark gap, and condenser was shown in CP-2410,
Figure 8. Later, this assembly was adapted to the oil-cooled hydrogen gap and built around the oil
tank as shown schematically in Figure 3.
A neon sign type transformer with a 5000 volt current limited (30 ma) secondary was found suf-
ficient to energize the spark circuit.









MDDC 1107


LUCITE CYLINDERS BAKELITE BACK

SECONDARY
BINDING POSTS


OIL TANK FOR
SPARK GAP


C-ONDENSER

---INSULATED
CONNECTOR
TO GAP





POLCAETELENE TO 5000 VOLT TRANSFORMER







Figure 3. Complete assembly of the high frequency spark ion source.


END OF DOCUMENT




UNIVERSITY OF FLORIDA


3 1262 0906 1225
N." ." j. u. .




Full Text
xml version 1.0 encoding UTF-8
REPORT xmlns http:www.fcla.edudlsmddaitss xmlns:xsi http:www.w3.org2001XMLSchema-instance xsi:schemaLocation http:www.fcla.edudlsmddaitssdaitssReport.xsd
INGEST IEID EJH7FOINL_FLNA70 INGEST_TIME 2012-02-29T17:17:53Z PACKAGE AA00009315_00001
AGREEMENT_INFO ACCOUNT UF PROJECT UFDC
FILES