"184" cyclotron synchroscope beam pictures on two probes

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UNITED STATES
ATOMIC ENERGY COMMISSION
OAK RIDGE
TENNESSEE


184" CYCLOTRON
SYNCHROSCOPE BEAM PICTURES ON TWO PROBES

by

Fred W. Yeater, Jr.


University of California





Published for use within the Atomic Energy Commission. Inquiries for additional copies
and any questions regarding reproduction by recipients of this document may be referred
to the Documents Distribution Subsection, Publication Section, Technical Information
Branch, Atomic Energy Commission, P. O. Box E, Oak Ridge, Tennessee.

Inasmuch as a declassified document may differ materially from the original classified
document by reason of deletions necessary to accomplish declassification, this copy does
not constitute authority for declassification of classified copies of a similar document
which may bear the same title and authors.


Date of Manuscript:

Document Declassifie


February 26, 1947

id: May 26, 1947


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This document consists of 4 pages.


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MDDC


184"


-987


CYCLOTRON


SYNCHROSCOPE BEAM PICTURES ON TWO PROBES


By Fred W. Yeater,


Experiment done by


Fred W


Yeater, Jr


Ralph Dufour


Albert Oliver


INTRODUCTION

The described experiment was performed in an effort to determine more definitely





that the peaks,


or "pips,


shown in synchroscope photographs of the beam current are


caused by precession of the beam.


EXPERIMENTAL SETUP


An auxiliary copper probe,


shielded for RF pickup,


was introduced into the main


vacuum tank through a Wilson seal on the port near the ion source in such a manner as to


generate a 1550 angle with the regular probe.


(See Figure 1.) This auxiliary probe was


made adjustable as to its radial depth, and equipped to supply a beam signal to the synchro-
scope in addition to that signal supplied by the regular probe.

Several photographs were taken in the usual manner under the following conditions:


Magnet current
Dee voltage (RF)
Capacitor speed
Pulse length


1500 amp
16 kv
240 rpm
5 microsec.


RESULTS


The usual beam pattern of two to three pips was obtained at several probe radii;
namely, 22 28 1/2 and 35 Then, when the auxiliary probe was positioned to catch
some of the accelerated ions, the beam pattern was altered to show the relative ampli-


tudes of beam current in the two probes


and the phase relation of those currents.


This effect is


shown most clearly in those photographs numbered 11 to 14,


(There were five additional photographs
not exist due to camera trouble.)


to complete this


inclusive.


series which unfortunately do


Following is a brief description of the photographs.
previously and the regular probe radius was 28 1/2" .


Operating values are as listed


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Photograph


Photograph


No. 11:


iNo. 12:


iNo. 13:


Photograph No. 14:


Note:


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Auxiliary probe radius
Beam current .55 x 10
This photograph shows
after the arc pulse (10


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S8'1/4
-' amp
the beam to be occurring 180 microseconds
microsecond markers).


Same conditions as above, but with expanded synchroscope sweep
showing the beam to be 25 microseconds in width.

Auxiliary probe radius 27 13/16"
Beam current .35 x o107 amp
The pips produced by the auxiliary probe are readily apparent,
as is the drop in beam current amplitude.

Auxiliary probe radius 27 9/16"
Beam current .25 x 10' amp
Beam current is more equally divided between the two probes, and
the phase relationship between these currents is more apparent.


In all the above photographs, the beginning of the synchroscope sweep was
triggered at a point on the RF cycle corresponding to a frequency of 11.06 me.


The remainder of this series would have shown the pips produced by the regular
probe to drop in amplitude while those produced by the auxiliary probe increased propor-
tionately as the radius of the auxiliary probe was decreased, until such time as the
auxiliary probe was catching essentially all the ions. At this time the pattern was a
series of triangular vanes of equal amplitude. This pattern actually changed very little,
if any, from that point where the current distribution was equal to the point where all the
current was on the auxiliary probe. The logical end result would have been a pattern
similar to the original, shown in Photograph No. 12, with a 155o phase shift.


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