PRESENT STATUS OF BOOSTER SYNCHROTRON UTILIZATION FACIL~TY AT KEKH. Sasaki
National Laboratory for High Energy Physics
Oho-machi, Tsukuba-gun, Ibaraki-ken, 305, Japan
Booster Synchrotron. Utilization Facility (BSF) was established in1978 to organize three experimental facilities; the pulsed neutron
source facility (KENS), the meson physics research facility (BOOM) andthe biomedical facility for cancer therapy and diagnosis (PARMS). The
500 MeV pulsed proton beam from the booster of the 12 GeV synchrotron iseffectively used for the researches of condensed matter and nuclearphysics with the produced neutrons and mesons. The construction of BSF
was completed in the spring of 1980, and the first beam from the booster
synchrotron was delivered to the facility in June of the year. The
operation time of BSF was 1,463 hrs in F.Y. 1980 and 2,883 hrs in F.Y.
1981, respectively. During two years scince the starting-up of thefacility, the operation of the facility was so reliable as to be around
90 % in the operation efficiency.
In the shared operation of the booster synchrotron with the mainring synchrotron, 42 pulses of the proton beam in maximum are availableto BSF every 2.5 sec, which is the repetition period of the 12 GeV
synchrotron. Each 50 nsec beam pulse contains about 6 x 10 11 protons.
The beam transmission including the extraction efficiency from thebooster was measured by comparing the beam intensity near the production
target with that of circulating beam in the booster. The results are
0.93 ± 0.06 in the machine time of the neutron scattering experiment and0.89 ± 0.10 in that of the meson experiment.
Neutrons produced with a tangsten target are moderated by two kindsof moderators; a polyethylene moderator at ambient temperature and asolid methane cold moderator at 20 K. The 4TI equivalent neutron peak
flux from KENS is plotted against neutron energy in Fig. 1 and is comparedwith those of two steady reactors.
We have a project called KENS-I' to increase the neutron flux by
one order magnitude without making significant modification of thetarget assembly and its shield. The increase will be achieved by improving
several factors as i) replacing the present W target by U238 target, ii)
increasing the proton beam current in the booster by making H- ion beaminjection, iii) adopting a groved moderator for the cold neutrons, etc.
In the best case, the increase will be achieved in 1985. There is also
a future project KENS-II to construct a new proton synchrotron of 800
MeV, which aims to increase the proton beam intensity by two orders ofmagnitude compared with that of the present booster 1 J.
The main apparatus in BOOM 2 ) is a pulsed muon channel, which ischaracterized by a superconductin g solenoid representing the TI~ decay
section. The superconductin g solenoid, which is 6 m long, 12 em indiameter and with a central field of 5 T, is indirectly cooled bysupercritical He. The number of ~+ produced in the pulsed muon channel
was estimated to be 3.5 x 10 4 /pulse or 7 x 10 5 /sec. For the~- intensity,-21-

those numbers should be diyided by a, facto:r: of 3. The compa:r:ison between
the negative muon factories is shown in Fig. 2. The instantaneo us
intensity is really huge, easily 3 orders of magnitude la:r:ger than thatof the LAMPF stopped muon channel. This fact promises the unique andfruitful researches of condensed matter with the pulsed ~SR.
The F.Y. 1981 was the first year for the regular open of the facility
to users in the field of neutron scattering experiments and meson science.
In the neutron scattering experiments , twenty-five experimenta l proposals
were approved, which covered a wide range in the research field ofcondensed matter and biological materials. In the meson experimenta lfacility, a research program on condensed matter with pulsed ~SR andnuclear physics with muons and pions has been commenced on the second
half of F.Y. 1981.
Constructio n of the facility building and installatio n of theexperimenta l facilities for biomedical use of the booster beam have been
finished. The first proton beam was introduced into the new beam lineof this facility in June of this year.
Reference
1)"Proceeding s of the meeting on BSF future prospects" edited by
T. Adachi, KEK Int. 82-6; T. Adachi, et al. "Proton Synchrotron
for Intense Neutron and Meson Beam" in this symposium.
2)
K. Nagamine, et al. "Meson Science Research with Pulsed Muons"in this symposium.

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AVERAGEINTENSITY

INSTANTANEOUS
INTENSITY

10'r~

I I:I104>"'u"'

KEKBOOSTER~c

U1~Eu:s10'~ 10'u

UJ~ 108~ 10z

UJ§~"' 1014 1--~LJ----t--+---t--"'--,tl-e-a...

LAMPFSIN</);zg 10'::::;:
106

LAMPF
(/)

z 100

TRIUMF::::>::::;:: KEK:·: BOOSTERnI
I

Fig. 1

Neutron spectrum~zz~SINII

TRIUMFtO'0.1

Fig. 2Comparison of negative
muon intensity