SPILL MONITOR FOR SLOW EXTRACTION
Y. Takeuchi, S. Ninomiya and K. Endo
National Laboratory for High Energy Physics
Abstract
This report describes the spill monitor used at present for
the tuning of extraction system. It displays the duty factor
giving the modulation level of the slow extracted beam and theextraction efficiency.
Low Frequency Structure of The Spill is observed by the secondary
emission chamber (SEC), placed at the downstream of the externalbeam line. This monitor has the bandwidth of d.c. ~ 15 KHz, andthe gain is adjusted to be lV per 10 12 extracted protons during
0.3 sec. The signal from this monitor is sampled at intervals of
100 ysec for 102.4 msec in the middle of the spill.
The duty factor is employed as a measure of the low frequency
structure in the spill signal, and is calculated by the formula 1 ' 2 )D

U6t(t)dt] 2
T J6t 2 (t)dt

X

100 (%),

where t(t) represent the low frequency burst waveform in theinterval of the measurement 0 < t < T.
In actual calculations, tne aoove integrations are converted
into the following expression
N[Z t(i)] 2DlX

100 (%)>

where N = 1024, and t(i) 's are the sampled data.
The duty factor of the spill (D) represents the reduction of
the spill time due to the modulation of the proton burst. Though
the duty factor cannot deal with the overall spill structure by
the limitation of the sampling time (102.4 msec), it is usufull
for the adjustment of the feed back control systems. In normal
operations the duty factor is about 90%.
Efficiency of Extraction
This system)employs a convenient method to measure the extraction efficiency 3 • Circulating proton numbers are sampled before
and after the slow extraction. The difference between the two is
the proton number to be extracted. The number of protons extracted
is measured by integrating the SEC signal andEfficiency

No. of prot. extracted
No. of prot. to be extractedX

100 ( %) •Accuracy
To minimize the measurement errors we used the attenuators,-177-having three steps -- x 1, x 1/4 or x 1/16, installed before thesampling circuits of each signals. The attenuators are adjusted
automatically according to the circulating proton number (Fig.
1,2). By this method an error peculiar to the circuits is within
1.6% for the proton number ranging from 8 x 10 9 ppp to 4.5 x 10 12ppp.
Accuracy of extraction efficiency is determined by that of
the intensity monitor and SEC. For the calibration of thissystem, we used another SEC which was calibrated within 5%. Total
error of efficiency displayed amounts to 8%.
The 8 data including the duty factor are averaged and theresults are also displayed.
Conclusion
Though the accuracy of the efficiency is not enough, thismonitor gives a measure of the performance of the extraction
system, and helps us to tune it.
Reference1)
2)
3)

D.B. Bloss et al. IEEE Trans. NS-18, 1971, p.973.
R.A. Andrews et al. Proc. of the IX th International Conf.
on High Energy Accel. (SLAC, 1974) p.456.
V.Ya. Gvozdev et al. Particle Accelerator Vol.6, 1974, p.53.
ATT.

SPILL INPUT

1V lld$.0.35

FIG. 1BLOCK DIAGRAM

3CQt-------1 DAC

GATE INPUTLED

DISPLAYPANELSPILL(SEC)

Fl G. 2

INTENSITY
GATE
1 sampling of prot. no. & attenuator select.
2 samplings of spill
3 sampling of prot. no.
SIGNALS AND TIMING-178-