Download Lithium and Boron beam acceleration through LINAC at PLF, Mumbai

LITHIUM AND BORON BEAM ACCELERATION THROUGH LINAC AT
PLF, MUMBAI
V. Nanal, R.G. Pillay, S. Pal, J.N. Karande, P. Dhumal, M.S. Pose, C. Rozario, M.E. Sawant,
A.N. Takke, A.A. Shinde, R.D. Deshpande, S.R. Sinha, A. Singh and S.P. Singh
Pelletron Linac Facility, TIFR, Mumbai – 400005.
Abstract
The superconducting LINAC booster at PLF has been
designed for A=12-60 and has been operational since
2007. Several experiments have been carried out using
beams of 12C to 35Cl. The QWR cavity is designed for
β0=0.1 and hence it is difficult to accelerate lighter beams.
Moreover, the low energy buncher system is not suitable
for beams lighter than 12C. Due to growing interest in
studying light ion (6,7Li, 10,11B) induced reactions on
fissile targets at energies higher than the available energy
from the Pelletron, we have recently accelerated beams
lighter than Carbon. The ion source deck was operated at
lower voltage (100-125 KV) for matching lighter beams
with low energy buncher. Both 7Li and 11B of
E~5 MeV/A obtained from the Pelletron were accelerated
through LINAC to E~8 MeV/A. The energy gain for
individual resonators was found to be consistent with
measured field values after correcting for transit time
factor. During the acceleration test with these light beams,
detail radiation dose mapping of the accelerator area and
surrounding area was carried out and found to be well
within permissible limits. Thereafter beams were
successfully delivered at target stations for experiments
with an intensity of 4-8 pnA.
BEAM ACCELERATION
Figure 1 shows layout of the LINAC. Timing
characteristics of the beam is monitored at entrance of
LINAC Phase I and Phase II, marked as Lin1 and Lin4 in
the Fig. 1. The ion source deck was operated at lower
voltage (100-125 KV) for matching lighter beams with
low energy buncher. Both 7Li and 11B of E~5 MeV/A
obtained from the Pelletron were accelerated through
LINAC to E~8 MeV/A. The energy gain for individual
resonators was found to be consistent with measured field
values after correcting for transit time factor.
INTRODUCTION
The superconducting LINAC booster, indigenously
developed to boost the energy of the heavy ion beams
from the 14 MV Pelletron accelerator at TIFR, Mumbai,
has been fully operational since July 2007 [1]. The
LINAC consists of seven modular cryostats, each housing
four lead plated quarter wave resonators, designed for an
optimum velocity β0=0.1 at an operating frequency of
150 MHz. Several experiments have been carried out
using beams of 12C, 16O, 19F, 28,30Si, 31P, 32S, 35Cl. It is
difficult to accelerate lighter beams and achieve good
transmission at target since for lighter beams β very
quickly exceeds the optimum velocity β0. Due to growing
interest in studying light ion (6,7Li, 10,11B) induced
reactions at higher energies and given the operational
limitations of Pelletron (12 MV), we have recently
extended LINAC operations to lighter beams [2] and
accelerated 7Li and 11B beam.
Figure 1: Layout of LINAC indicating positions of timing
detectors at entrance of Phase I and Phase II
Time spectra measured with 1” BaF2 during the Boron
beam acceleration at Lin1 (Phase I entry), at Lin4
(Phase II entry) and at user station are shown in Figure 2.
The measured FWHM (<1 ns) is inclusive of detector
resolution. Nearly identical time structure of at Lin1 and
Lin4, not only ensured good acceptance in phase II but
also resulted in good transmission. Both Lithium and
Boron beams were successfully delivered at target
stations for experiments with an intensity of 4-8 pnA.
During the acceleration test with these light beams, detail
radiation dose mapping of the accelerator area and
surrounding area was carried out and found to be well
within permissible limits. The operational limit of
E≤8 MeV/A with a maximum of 10 pnA current at target
has been imposed from the radiation safety
considerations.
SUMMARY
The LINAC operations have been successfully extended
to beams lighter than A=12. The ion source deck voltage
is lowered for better matching of lighter beams into low
energy buncher. Starting with E~5 MeV/A 7Li and 11B
beam from the Pelletron, were accelerated through
LINAC to E~8 MeV/A and were successfully delivered at
target stations for experiments. The operational limit of
E≤8 MeV/A with a maximum of 10 pnA current at target
has been imposed from the radiation safety
considerations.
ACKNOWLEDGMENT
We would like to thank the Pelletron-LINAC staff,
DNAP, Low Temperature Facility, Central Workshop and
Electronics Division (BARC) for their support.
REFERENCES
[1] R.G. Pillay,
Figure 2: Time structure of 11B beam at various locations
measured with BaF2.
“Overview of the Pelletron Linac
Facility”, InPAC2011 proceedings.
[2] V. Nanal et al.,“Extension
of
Superconducting
LINAC
Operation
to
Lighter
Beams”,
http://accelconf.web.cern.ch/AccelConf/HIAT2012/pa
pers/po06.pdf