Beam dynamics study and design of 348° compression magnet for neutron time of flight (n-TOF) facility

Abstract

A n-TOF experiment requires 1 nsec duration pulses to get better energy resolution. The paper presents the design of a compression magnet that can compress a 10 nsec electron pulse to ∼ 1 nsec having energy variation from 18–30 MeV. A zero gradient, 5-sector magnet that will bend the beam through 348° is designed for the same. The beam dynamics to calculate energy spread, design of sector magnet and the simulation results of CST particle studio are presented. A combination of magnetic fields 0.1 T, 0.05 T and 0.02 T in different sectors of the magnet give the compressed pulse width of ∼ 1.3 nsec.

9-sector compression magnet design

“…Figure 2 shows the energy distribution of 30 different micropulses within a macropulse of 30 MeV linac. The compression magnet is designed taking into account this energy variation from 18 MeV to 30 MeV [2,3].…”

“…Assuming 100% transmission in the magnet, a current in the output pulse is increased accordingly. In order to compress the 18-30 MeV, 10 ns, 10 A electron macro pulse to 18-30 MeV, 1 ns, 100 A (compression ratio 10:1), a magnetic field, B = 0.1 T is required [2,3].…”

“…Figure 3 shows the electron trajectory in the magnet at different energies. The beam transmission through magnet is ~100% [2,3].…”

“…It will rotate second time and will exit from sector S 5 . Analytical treatment of 9-sector magnet is same as 5-sector magnet as described in references [1][2][3][4]. An electron beam is injected from a point 'A' that is at a distance,'d' from the origin 'O'.…”

Development of 5-sector, 360̂compression magnet for electron Linac

“…The calculated energy spread between first and the last micropulse is ∼ 40%. A compression magnet utilizes this time-energy relationship to further compress a pulse to 1 ns [2].…”