Beam test of a new radio frequency quadrupole linac for the Japan Proton Accelerator Research Complex

We performed a beam test of a new radio frequency quadrupole linac (RFQ III) for the beam current upgrade of the Japan Proton Accelerator Research Complex. First, the conditioning of RFQ III was conducted, and after 20 h of conditioning, RFQ III became very stable with a nominal peak power and duty factor of 400 kW and 1.5%, respectively. An off-line beam test was subsequently conducted before installation in the accelerator tunnel. The transmission, transverse emittance, and energy spread of the 50-mA negative hydrogen beam from RFQ III were measured and compared with simulation results. The experiment and simulation results showed good agreement; therefore, we conclude that the performance of RFQ III conforms to its design.

Figure 1

Schematic of the RFQ test stand (top view).

Figure 2

Photograph of J-PARC RFQ III installed in the test stand.

Figure 3

Photograph of the test bench.

Figure 4

Conditioning history of RFQ III.

Figure 5

Phase space distribution of the ion source measured just after the SM1 of the ion source test stand.

Figure 6

Measured and simulated transmissions of RFQ III as functions of the intervane voltage $V_n$.

Figure 7

Measured (upper row) and simulated (lower row) transverse emittances of RFQ III. The absolute positions of the emittance monitors are not fully calibrated.

Figure 8

Typical wave form of the $500\mu \mathrm{s}$ pulse operation. Repetition rate of this operation was 5 Hz.

Figure 9

Profiles of the beams having passed through the slits (SL) and bending magnet (BM). The solid histogram is the profile when the BM is set to 0 A (straight beam), and the hatched histogram is that when the BM is set to 84 A (bended by 15 degrees). The peak positions of each histogram are adjusted to overlay.

Figure 10

Longitudinal emittances and energy spreads at the exit of RFQ III, where the simulation results are given in (a), (b), (d), (e), (g), and (h), and the measured and simulated transverse beam profiles at the EMSLx are given in (c), (f), and (i) for $\mathrm{BM}=84\mathrm{A}$. Exp. and Sim. denote the experiment and simulation results, respectively.

Figure 11

Measured and simulated beam widths at the EMFCx as functions of $V_n$. The simulated energy spreads at the RFQ exit are also shown.