The 9th Symposium on Accelerator &ience and Technology, Tsukuba, Japan 1993

Response of KEK Secondary Emission Chamber to Several GeV Protons and Deuterons
M. Ieiri, M. Minak:awa, H. Noumi, Y. Yamanoi, Y. Kato, H. Ishii, K. H. Tanaka, Y. Suzuki, M. Tak:asak:i,J. Chiba, M. Numajiri, T. Miura, T. Suzuki and K. Kondo
KEK, National Laboratory for High Energy Physics, Oho 1-1, Tsukuba, Ibarak:i 305 Japan

Abstract
We have investigated the response of KEK secondaryemission chamber for protons at 4, 5 and 12 GeV, and for
deuterons at 7, 8 and 10 Ge V. The response was measured
both by the "foil activation" technique and by secondary pions
produced from a carbon target0I

100 (mm)
II. INIRODUCTION
A ~ndary ~ission !;hamber (SEC) is one of usefuldetectors for the beam intensity in several GeV [1]. In theslow extracted beam lines of 12GeV proton synchrotron atKEK (KEK-PS), SECs are installed at several positions suchas just downstream of the extraction from the accelerator andjust upstream of the production target stations, in order toEach SEC has beenmonitor primary beam intensity.
calibrated by the "foil activation" method once or twice a year
[2].
The KEK-PS has been operated as a proton machine up
to 12 GeV for a long time. Recently, however, deuteron canbe also accelerated up to 11.2 GeV [3] and the experiments
using deuteron beams have been performed [4]. SECs havebeen calibrated for deuterons as well as protons at several
energies.
In this report, the structure and basic characteristics ofthe KEK SEC are presented in the section II, and the response
measurement of the KEK SEC to protons and deuterons isdescribed in the section III. The results and discussion aredescribed in sections IV.

II. KEK SEC

AI foil

Front view

Side view
Figure 1.

A schematic drawing of the KEK SEC

1.2

.....

'"''"':c<'"'

-...

,.,

..

1.0 0"""'"" '\J '.I~-~

b0.8
0.6

hA. Structure
0.4

A schematic drawing of the KEK SEC is shown in fig.
1. 5 aluminum foils for signals and 6 aluminum foils for
positive high voltages are assembled alternately with 8 mmspacing in a vacuum chamber. Each aluminum foil is 7 J.l.m
thick and is plated with 0.1 J.l. m thick silver by a sputtering
technique. A chamber is finally evacuated by an ion pump up
to about 10·7 Torr. Charges from a SEC are collected by adigital current integrator (ORTEC 439) at "1 pulse/10.10
Coulomb" mode.

B. Counting efficiency as a function of the supplied voltage
The counting efficiency of the SEC for 12 GeV protons
changes as a function of the voltage supplied between foils asshown in fig. 2. In this measurement, two SECs were
installed in the beam line in cascade. Charges from a SEC
were measured with changing supplied voltages, whereas

0.2
0.00Figure 2.

100200300400600500(volts)

The counting efficiency of the SEC as afunction of the supplied voltage.

another SEC was used as a beam intensity monitor at a fixedvoltage. The curve has a peak at around 50 V and shows asame feature as in ref. [5]. The efficiency decreases very
slowly as the supplied voltage increases in the region ofabove 60 V. This slope is small and about 1 %/100 V. Inthe usual operation, the supplied voltage is set at 100 V.

-477-C. Position dependence

4The curve in fig. 3 shows the SEC counting dependence
on the incident position of 12 GeV protons. Response of a
SEC was measured with changing beam position by using asteering magnet. The beam spot was smaller than 10 mm indiameter. Incident beam position and size were monitored bya ~gmented J!arallel-plate ion ~hamber (SPIC) [6]. Another
SEC installed upstream of a steering magnet monitored abeam intensity. The response of SEC is found to be almost
flat within the area of 80 mm in diameter. The beam sizes atany places where SECs locate are sufficiently small
comparing with this effective area (80 mm in dia.) of theSEC.

00001oo 00000-60-40-2000020040

position

III. RESPONSE MEASUREMENT OF SEC

Figure 3.

SEC response dependence on incident beam
position

Figure 4.

A layout around the T3 beam line

A. calibration by foil activation
In order to get the absolute response for protons anddeuterons, the calibration by the "foil activation" method has
been performed for the B3-SEC which locates just upstreamof the target station of the T3 beam line in fig. 4.
A stack of aluminum foils, which area was lOx 10 cm 2 ,was attached to the SEC and exposed to primary beams. A
sample aluminum foil of 25 11m thick was sandwiched by thesame aluminum foils in order to compensate the loss of
produced radioactive nuclei. A "rad color" was also stacked
together with aluminum foils to monitor an integrated beam
size at exposure. Exposure times were ranged from 7 min. to37 min. depending on primary beam intensity.
Thecalibration was performed at 4, 5 and 12 Ge V for protons and7, 8 and 10 GeV for deuterons. Counts of a current integrator
connected to the SEC were accumulated during the exposure.
After the exposure, a stack of foils was punched together
with an attached "rad color" which changed its color at aroundbeam exposed area. To determine punched sizes, threedifferent areas were punched and measured its activities forbo th 24Na and 1 Be. The first area (A) was 1 mm larger than adiscolored ellipse of the "rad color", the second area was 40mm in diameter of the remaining foil and the third was theremaining. About 98 % of produced activities were found in
the area A, and more than 99 % were observed within the areaof 40 mm in diameter. A punched size was thus determinedso as to cover the exposed area.

The 24Na activities were determined by assaying theintensity of the 1368 keV y-ray with a pure Ge detector. The
results obtained are shown in table 1. Errors indicated include
the counting efficiency of a pure Ge detector (<5% ), statisticalerrors (<1 %) and uncerl:ainty of an aluminum foil thickness(<1%).
The cross sections used for the activities 24Na via
27 Al(p,3pn) or 27 Al(d,3p2n) reactions are listed in table 2 [7].
The sensitivity of the KEK SEC to deuteron seems to be
40-50% higher than to protons.

Table 1 Results of the foil activation method
Incident Energy
Particle[GeV]
d10d87d4pp5p1260(mm)

ExposureDate(in 1992)
Time

Number of incident
particle by ~a10-APR
15-APR
21-APR
19-MAY
21-MAY
9-JUN

10:47-11:18
10:54-11:10
10:37-10:48
11:05-11:25
10:43-11:20
10:55-11:02

1.21±0.06
1.48±0.08
0.93±0.05
1.73±0.09
1.41±0.07
1.49+0.08(xiO'":J-478-

Integrated charge
from SEC
[llC]
4.75
5.36
3.63
4.57
3.62
4.22

SEC charge per1014 particles
[jlC]
3.93
3.62
3.90
2.64
2.57
2.83

As for proton induced reactions, there are several
independent measurement for the ~a activities in GeV
region, however, only two data for ~a at 2.33 GeV and 7.3
GeV are available for deuteron [8]. If a SEC's response foris 24the same as for protons , cross section of thedeuterons
1:1
Al(d,3p2n) Na reaction should be about 11 mb in thisenergy region. Further investigations of this monitor reaction
for deuteron would be awaited.

Table 2 Cross sections for 24Na production
Cross sections used for 24Na
Particle Energy
[mb]
[GeV]
15.
9.0
8.8
7.92

7,8,104512dppp

B. calibration by secondary pions

Secondary produced pions (7t±) for a carbon target of 40
mm thick, which locates just downstream of the B3-SEC
were measured during E257 experiment at the T3 beam line. 'Preliminary values of pion yields normalized to 100 counts of
the B3-SEC (10-8 Coulomb) are listed in table 3. In thismeasurement and analysis, there were no large uncertainties inabsolute values to extract pion yields between protons anddeuterons. On the assumption that a proton and a neutron ina deuteron of several GeV react with target nuclei
independently, sum of 1t+ and 1t- yield by incident protons
should be equal to 1t+ or 1t- yield by incident deuterons at thesame incident energy per nucleon. The energy in several GeVregion would be high enough above the pion production
threshold, and the deuteron binding energy is negligibly small
compared to this energy region. The numbers in the next
columns of 1t+ or 1t- yields by deuteron are the deduced
incident deuteron intensity normalized proton intensity
obtained from the sum of 1t+ and 1t- yield by protons at thesame incident energy under the above assumption. For thismeasurement, the response of SEC is almost the same for
proton and for deuteron.

For data of secondary pions, we would like to express
our thanks to the E257 experimental group for their kindcooperation. We are also grateful to the KEK-PS acceleratorgroup for their support to the measurement.

V. REFERENCES

IV. RESULTS AND DISCUSSION[1] V. Agoritsas and R. L. Witkover, "Test of SEC
Stability in High Flux Proton Beams", IEEE Trans. on
NS, Vol. NS-26, pp.3355-3357, June 1979.
[2] J. B. Cumming, "Monitor Reactions for High Energy
Proton Beams", Ann. Rev. Nucl. Sci., Vol. 13, pp. 261-286, 1963.
[3] Y. Mori et al., "Acceleration of Deuteron Beam in the
KEK Proton Synchrotron", KEK Preprint 91-159.
[4] KEK-PS proposals E235 (spokesperson: M. A. Kovash)
and E257 (spokesperson: J. Chiba); J. Chiba et al.,"Enhancement of Subthreshold Antiproton Productionsin Deuteron Induced Reactions", Nucl. Phys. A553,
pp.771c-774c, 1993.
[5] V. J. Vanhuyse et al., "Secondary Beam Emission
Monitors for 0.5 to 3.5 MeV Electrons", Nucl. Instr. andMeth. 15, pp.59-62, 1962 ; D. B. Isabelle and P. H.
Roy, "Factors Influencing The Stability of a Secondary
Electron Monitor", Nucl. Instr. and Meth. 20, pp. 17-2

By the foil activation method, the KEK SEC seems tohave 40 - 50 % higher sensitivity to deuteron than toprotons, however, there are no such large difference between
responses to proton and deuteron from the consideration of
secondary pion yields. The response of the SEC should beoriginated from the atomic process and should be a function ofvelocity {j3) of incident particles. Since ~s of proton anddeuteron are almost the same in this energy region, theresponse for deuterons is likely to be the same as for protons.

0, 1963.
[6] K. H. Tanaka et al., "Improvement in the Profile andEmittance Measurement System of the KEK-PS External
Beam Line", KEK Preprint 91-27.
[7] M. Numajiri, KEK internal report (These are obtained
under smooth energy dependence of measured values.)[8] J · Banaigs et al., Nucl. Instr. and Meth. 95, pp. 307-3
11, 1971 ; P. Kozma and J. Kliman, J. Phys. G: Nucl.
Part. Phys. 16, pp. 45-53, 1990.

Table 3Incident
Energy[GeV/u]
5.0

4.0

3.5

Yields of pions normalized to 10-8 Coulomb of SEC (Preliminary)
Number of produced 1t by deuteron
Number of produced 1t by proton
Momentum++d-in tensity
7t
d-in tensity
7t
sum
7t
7t
of produced 1t[xl03][x103][x 103][x103][xl03][GeV/c]
1.0
1.5
2.0
2.5
1.0
1.5
2.0
1.0
1.5

196
442
438
309
(173)
(347)
212
137
210

107
170
143
110
76
101
71
48
53

294
585
571
389
213
351
250
206
288

303
612
581
419
250
449
283
185
264

-479-

0.97
0.96
0.98
0.93
0.85
0.78
0.88
1.11
1.09

296
625
580
400
205
353
265
189
283

0.97
1.02
1.00
0.95
0.820.79
0.94
1.02
1.07