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Experimental study of resonance crossing
Nuclear Physics B (Proc. Suppl.) 155 (2006) 332–333 www.elsevierphysics.com
Experimental study of resonance crossing S. Machida, Y. Hashimoto, KEK Oho, Tsukuba-shi, Ibaraki, 305-0801, Japan and T. Uesugi, NIRS Inage, Chiba-shi, Chiba, 263-8555, Japan 1. Introduction Although non-scaling FFAG is one of good candidates to accelerate muons in Neutrino factory accelerator complex [1], it is not clear if it works as expected. Without chromaticity control, tune changes quite a lot during acceleration. A beam crosses many linear and nonlinear resonances. Question is if there is any deterioration in the beam quality. There is a proposal to make a small machine to test the principle [2]. Non-scaling FFAG consists of ordinary quadrupole and dipole magnet. It is nothing but a storage ring in that respect. If there is an adequate aperture in horizontal direction, it should be possible to test the resonance crossing in existing storage rings or synchrotrons with constant magnetic fields. This paper describes an attempt to do such experiment using HIMAC synchrotron. 2. HIMAC as a non-scaling FFAG HIMAC is a synchrotron for heavy ion therapy in Chiba. Its horizontal aperture is about 0.2 m and dispersion is 3 m so that a beam with momentum spread of a few percents can be accepted. Initial transverse emittance is controlled at the injection. HIMAC has a fancy beam profile monitor based on the interaction between a beam and a sheet beam injected perpendicularly as shown in Fig. 1. Beam profile in x-y real space can be obtained with almost time resolution of RF frequency. Operation without synchronization of magnetic fields and with increase of RF frequency gives similar beam dynamics as non-scaling FFAG. Initial tune just above νy=3.5 is chosen so that a little acceleration causes crossing of the half-integer resonance. 0920-5632/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysbps.2006.02.091
Figure 1: Sheet beam profile monitor.
3. Experiments First, we measured the beam position shift in horizontal direction due to acceleration. Figure 2 shows a projection of the beam profile monitor. A peak of the profile moves leftward about 10 mm in 40 ms. It agrees with the dispersion function at the monitor and frequency shift in 40 ms. Note that the dip at the center is due to less sensitive CCD channels and does not reflect real profile.
Figure 2: Shift of beam position due to acceleration.
S. Machida et al. / Nuclear Physics B (Proc. Suppl.) 155 (2006) 332–333
333
We also measured width of the half-integer resonance with beams. From Fig. 3, it is estimated about 0.02.
Figure 5 shows images of profile at each time step and, as a summary, Fig. 6 shows measured beam width and intensity as a function of time.
Figure 3: Measured resonance width at νy=3.5.
Figure 5: Evolution of beam profile and intensity.
After those checks of basic parameters of the synchrotron, we measured evolution of beam profile and beam intensity when the beam crosses the half integer resonance. RF frequency was increased by 26 kHz/s that gives the change of vertical tune of – 0.0005 /ms. Beam was injection at the tune above the resonance by +0.033. Figure 4 (a) shows beam intensity when the beam crosses the resonance. As a comparison, Fig. 4 (b) is one without crossing by injecting below the resonance.
Beam is injected at 40 ms from the machine trigger (horizontal axis is time from the trigger), and crosses the resonance at about 20 ms later. Although beam loss at 50 ms is clearly caused by resonance, only a slight beam blow up is observed. We plan to do the same experiment again in near future.
(a)
Figure 6: Vertical beam size (above) and intensity (below).
4. Summary
(b)
Figure 4: Beam intensity with (a) and without (b) crossing.
Although beam loss about 50 ms after injection (50 ms/div.) can be attributed to other reasons, difference between two figures at about 20 ms after injection is manifest.
Experimental simulation of non-scaling FFAG is possible using ordinary synchrotron like HIMAC. We measured beam profile and intensity when a beam crosses a half-integer resonance in that simulated non-scaling FFAG. At the moment, manifest beam loss due to resonance crossing is the only evidence and deterioration of emittance was not observed. References [1] C. Johnstone and S. Koscielniak, Workshop on High Intensity and High Brightness Hadron Beams (HB2002), W. Chou et. al. eds. AIP Conference Proceedings, p. 207 (2002). [2] R. Edgecock for the EMMA Collaboration, Proceedings of NuFact05, 2005.
Experimental study of resonance crossing S. Machida, Y. Hashimoto, KEK Oho, Tsukuba-shi, Ibaraki, 305-0801, Japan and T. Uesugi, NIRS Inage, Chiba-shi, Chiba, 263-8555, Japan 1. Introduction Although non-scaling FFAG is one of good candidates to accelerate muons in Neutrino factory accelerator complex [1], it is not clear if it works as expected. Without chromaticity control, tune changes quite a lot during acceleration. A beam crosses many linear and nonlinear resonances. Question is if there is any deterioration in the beam quality. There is a proposal to make a small machine to test the principle [2]. Non-scaling FFAG consists of ordinary quadrupole and dipole magnet. It is nothing but a storage ring in that respect. If there is an adequate aperture in horizontal direction, it should be possible to test the resonance crossing in existing storage rings or synchrotrons with constant magnetic fields. This paper describes an attempt to do such experiment using HIMAC synchrotron. 2. HIMAC as a non-scaling FFAG HIMAC is a synchrotron for heavy ion therapy in Chiba. Its horizontal aperture is about 0.2 m and dispersion is 3 m so that a beam with momentum spread of a few percents can be accepted. Initial transverse emittance is controlled at the injection. HIMAC has a fancy beam profile monitor based on the interaction between a beam and a sheet beam injected perpendicularly as shown in Fig. 1. Beam profile in x-y real space can be obtained with almost time resolution of RF frequency. Operation without synchronization of magnetic fields and with increase of RF frequency gives similar beam dynamics as non-scaling FFAG. Initial tune just above νy=3.5 is chosen so that a little acceleration causes crossing of the half-integer resonance. 0920-5632/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysbps.2006.02.091
Figure 1: Sheet beam profile monitor.
3. Experiments First, we measured the beam position shift in horizontal direction due to acceleration. Figure 2 shows a projection of the beam profile monitor. A peak of the profile moves leftward about 10 mm in 40 ms. It agrees with the dispersion function at the monitor and frequency shift in 40 ms. Note that the dip at the center is due to less sensitive CCD channels and does not reflect real profile.
Figure 2: Shift of beam position due to acceleration.
S. Machida et al. / Nuclear Physics B (Proc. Suppl.) 155 (2006) 332–333
333
We also measured width of the half-integer resonance with beams. From Fig. 3, it is estimated about 0.02.
Figure 5 shows images of profile at each time step and, as a summary, Fig. 6 shows measured beam width and intensity as a function of time.
Figure 3: Measured resonance width at νy=3.5.
Figure 5: Evolution of beam profile and intensity.
After those checks of basic parameters of the synchrotron, we measured evolution of beam profile and beam intensity when the beam crosses the half integer resonance. RF frequency was increased by 26 kHz/s that gives the change of vertical tune of – 0.0005 /ms. Beam was injection at the tune above the resonance by +0.033. Figure 4 (a) shows beam intensity when the beam crosses the resonance. As a comparison, Fig. 4 (b) is one without crossing by injecting below the resonance.
Beam is injected at 40 ms from the machine trigger (horizontal axis is time from the trigger), and crosses the resonance at about 20 ms later. Although beam loss at 50 ms is clearly caused by resonance, only a slight beam blow up is observed. We plan to do the same experiment again in near future.
(a)
Figure 6: Vertical beam size (above) and intensity (below).
4. Summary
(b)
Figure 4: Beam intensity with (a) and without (b) crossing.
Although beam loss about 50 ms after injection (50 ms/div.) can be attributed to other reasons, difference between two figures at about 20 ms after injection is manifest.
Experimental simulation of non-scaling FFAG is possible using ordinary synchrotron like HIMAC. We measured beam profile and intensity when a beam crosses a half-integer resonance in that simulated non-scaling FFAG. At the moment, manifest beam loss due to resonance crossing is the only evidence and deterioration of emittance was not observed. References [1] C. Johnstone and S. Koscielniak, Workshop on High Intensity and High Brightness Hadron Beams (HB2002), W. Chou et. al. eds. AIP Conference Proceedings, p. 207 (2002). [2] R. Edgecock for the EMMA Collaboration, Proceedings of NuFact05, 2005.