This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Ball, M.

Caussyn, D.D.

Ellison, T.

Hamilton, B.

Yoder, N.

English

IUScholarWorks

A BEAM TRACKING SYSTEM FOR USE IN ORBITAL DYNAMICS STUDIES 
M. Ball, D.D. Caussyn, T. Ellison, B. Hamilton, and N. Yoder 
Indiana University Cyclotron Facility, Bloomington, IN 47408 
The extremely small emittance (< 0.05 rpm) and momentum spread (< 1 x 
of the electron-cooled proton beams makes the IUCF Cooler Ring an ideal laboratory for 
the study of nonlinear beam dynamics with very high resolution. Various beam diagnostic 
methods are being developed for use in an upcoming series of nonlinear beam dynamics 
experiments using the Cooler Ring. The measurement of the evolution of the beam in 
phase space is the one with the highest priority. 
A data acquisition system is being developed to track the position of a single beam 
bunch in transverse phase space on a turn-by-turn basis in the Cooler. This system consists 
of four major subsystems: (1) the front-end electronics, (2) the level control with signal 
conditioning, (3) the sample and hold (S/H) module and (4) the digitizer. 
The front-end electronics consists of two existing beam position monitor (BPM) elec- 
trodes. For each electrode, amplifiers produce signals proportional to the beam intensity 
and the product of the beam position and intensity. The signal peak voltage is used in 
a feedback loop to adjust programmable 10 dB step attenuators with 10 increments to 
increase the dynamic range. After the attenuators, the short pulses (5-10 ns in length) are 
peak-detected by a passive RC circuit having a switch-selectable decay time to minimize 
errors due to timing jitter as they are sampled. The S/H modules use high speed S/H 
amplifiers having a 12 ns track-to-hold settling time. The output of two S/H modules are 
fed into a 2: 1 analog multiplexer enabling a single digitizer to record both the position and 
intensity signals; the S /H electronics also reduce the required digitizer speed. The trigger 
clock for the S/H modules operates off the beam intensity signal and runs at the pulse 
repetition frequency divided by the rf harmonic number, which may be as large as 2.2 
MHz. Transient recorders (TRs) with 12 bit resolution and 8192 channel sample buffers 
are used as the digitizers. 
The TR is a CAMAC module which interfaces to the VAX network, allowing the use 
of IUCF data aquisition software to control the data aquisition and record the data. This 
has reduced the amount of software development necessary and produces some flexibility 
when making additions. It also allows various online analysis functions to be performed, 
such as calculating a fast Fourier transform (FFT) of the normalized beam position, or 
producing two dimensional histograms of the horizontal beam position at the two different 
BPM electrodes (xl vs. x2). 
This system has been tested using a 45 MeV proton beam. When the beam is kicked 
using a a horizontal kicker magnet, a coherent betatron oscillation of a beam bunch is 
induced. An FFT of the beam position from either BPM after the kick yields the fractional 
tune, as shown in Fig. 1. A PoincarB map, or phase space map, can also be generated from 
the data acquired by this system. Online, a simple plot of XI vs. $2 on a turn-by-turn 
basis is representative of a phase space plot, an example of which is shown in Fig. 2. 
The system signal to noise is determined by the input noise in the first amplifier 
(0.5 nv/&) and the electrode sensitivity ( V/IPeakx), about 0.2//? n/mm. Consequently, 

operating with peak currents (the product of current and bunching factor) of about 100 PA, 
a bandwidth of about 100 MHz, and a value for P = v / c  of 0.3, we expect rms noise of 
less than 0.1 mm. Although normalized beam position resolutions of 0.13 mm have been 
observed, more systematic testing is needed. The system has demonstrated a 1% amplitude 
linearity over the 10 dB step attenuator range. Since the trigger circuitry operates directly 
off of the beam signals, no adjustments are required with varying beam velocity, harmonic 
number, bunching factor, or intensity. 
CObIPLETION OF T-SITE CONSTRUCTION FOR EXPERIMENT CEO3 
C. C. Foster, G. P. A. Berg, T. Rinckel, and E. Lincicome 
I n d i a n a  Un ive r s i t y  Cyc lo t ron  Facili ty,  Bloornington,  I N  474 08 
The 6" bending magnet and vacuum chamber for the CEO3 experiment (p+p-+ 
p+n+?r+) was assembled, carefully field mapped over a large volume, integrated to the gas 
jet target box, installed and aligned at the T-site, and tested. Experiment CEO3 has com- 
pleted several runs with this facility, which are described elsewhere in this report. There 
are several approved experiments which plan to use this facility for recoil experiments. 
Experiment CEO6 is the first of these. For this experiment, a detector vacuum chamber 
to enclose a special array of detectors is being built to attach to the thin window exit of 
the 6" vacuum box on the inside of the ring. The details of this experiments are discussed 
elsewhere in this report. 
The 6" magnet is essentially a small-angle spectrograph which permits ejectile exit 
angles up to 54" towards the inside of the ring and up to 30" towards the outside for 
particles of high rigidity, or for negative ejectiles. The fully usable area of the gap is 33 cm 
wide by 12.7 cm high, over the entire length of 34.3 cm. An extensive map of the magnetic 
field has been made, with and without an upstream field clamp, which will be necessary 
for planned use with a polarized 3 ~ e  target. The field differs in the fringe field areas from 
a TOSCA calculation. The maximum rampable magnet field is 0.38 Tam, suitable for 
bending 500 MeV protons. The maximum field in the center of the gap is 0.75 T. 
As a result of the larger acceptance requirements in this region of the new ring tune, 
the exit pipe of the vacuum box was enlarged to 29 mm square at the exit of the box 
tapering to 36 mm square at a distance of 22.37 in downstream at the exit junction of the 
pipe. This pipe limits how close to the beam detectors may be placed. For further details 
of the features of this facility see the description in the May 1988-April 1989 Scientific and 
Technical Report of the Indiana University Cyclotron Facility. 


A Beam Tracking System for Use in Orbital Dynamics Studies

https://scholarworks.iu.edu/dspace/bitstream/2022/692/1/iucf1990-1991_175-177.pdf

A Beam Tracking System for Use in Orbital Dynamics Studies

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