A noninterrupting method for measuring a charged particle beam current consisting of a series of periodic pulses is presented. The pulsed beam is allowed to pass through a high permeability toroid on which is wound a multiturn coil. If the distance traveled by a beam particle during one pulsing period is large compared with the toroid dimensions, then the voltage induced in the coil consists of a series of impulses, the time integral of each impulse being proportional to the beam current. Since this voltage is equal to that induced in the coil by a one‐turn loop wound on the toroid and carrying a current identical to the beam current, it is possible to vary this current, and employ the multiturn coil as a null indicator to indicate equality of the beam and loop currents. If now a capacitor adjusted to resonate with the multiturn coil is placed across the coil, the sensitivity of the null circuit is increased by a factor equal to the Q of the resonant circuit. Using this resonant magnetometer and a 1000‐cps chopping rate, currents of 3×10−7 A peak have been measured with an accuracy of ±10−8 A.

1.
K. T.
Dolder
,
M. F. A.
Harrison
, and
P. C.
Thonemann
,
Proc. Roy. Soc. (London)
A264
,
367
(
1961
).
Google Scholar
 
2.
W. S.
Whitlock
 and
C.
Hilsum
,
Nature
185
,
302
(
1960
).
Google Scholar
Crossref
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3.
The first nonzero harmonic, the third, is smaller than |Vc| by a factor of 1/9Q0. In general, if the kth harmonic is nonzero it is smaller than |Vc| by a factor of at least 1/k2Q0.
4.
W. C. Lineberger, Master’s thesis, Georgia Institute of Technology, 1963, Appendix II.
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© 1963 The American Institute of Physics.
1963
The American Institute of Physics
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