The Multi-Harmonic Single Gap Buncher, operating at the bunching frequency
of 12.125 Mhz and its harmonics, can provide a pulsed beam of
more than 50%
bunching efficiency. 7Li, 12C, 16O, 28Si, 31P and 58Ni beams were bunched
by using
this multi harmonic bunchers. The typical time resolution achieved
is between
1 to 2 ns. Other beams can also be bunched.
SALIENT FEATURES OF THE MULTI-HARMONIC BUNCHER
*It consists of three major parts
1) The Mechanical assembly
2)The Tank Circuits (12.125MHz, 24.25MHz,36.375MHz)
3)The Electronics
*It is a single -gap buncher
Bunching done across a closely spaced pair of grids
*It uses a saw-tooth voltage for bunching
The saw-tooth is approximated with 3 sine-waves
The travelling wave deflector is used for delivering beams of different repetition rates between 250 ns to 2 µs. The chopper is also used with the TWD. There is also a high energy sweeper to reduce dark current.
Chopper of NSC beam pulsing system is basically a pair of plate. 4 MHz
RF is applied across this pair of plate with a dc offset. This deflects
the beam particles on x - axis and only a small portion of beam (chopped
beam) will appear at its output at a fixed interval of 250 ns. Time resolution
of chopped beam will depend upon the amplitude of RF signal and its dc
offset value. Travelling Wave deflector is a twelve pair of plates.
Whenever it switch on, +200Vdc will appear on upper plates and -200Vdc
on lower plates of all pairs. This field of 400Vdc across each pair will
deflect the beam in x - axis away from beam path. If somehow a negative
pulse of 200V is applied to upper plate and positive 200V applied to lower
plate of a single pair simultaneously, beam will not experience any deflection.
If these pulses (-200V and +200V) are applied to all 12 pair of plates,
a portion of chopped beam will appear at TWD output. The repetition rate
of chopped beam at TWD output will be equal to the frequency of the pulses
applied to pair of plates.