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This paper describes the beam commissioning progress of the 7 MeV H − linac injector for the proton synchrotron of Xi'an 200 MeV Proton Application Facility (XiPAF). To fulfill a flux of 105 ∼ 108p/cm2/s with a uniformity better than 90% on a 3 cm × 3 cm sample size at the experimental station, the number of the accumulated protons in each cycle in the synchrotron is designed to be larger than 2 × 1011. The protons are acquired from the H − beam stripped by the carbon foil, which enables transverse space painting during injection. The maximum pulse length of the injected beam is 40 μ s. With an estimation of 40 for the intensity gain factor, the injected beam is required to have a peak current of higher than 1 mA, with the normalized transverse emittance of 90% particles less than 6 and 4 π mm mrad for the horizontal and vertical planes, respectively, and the momentum spread of 90% particles within ± 0.45%. The injector mainly consists of an H − ion source, a low energy beam transport line (LEBT), a 3 MeV radio frequency quadrupole (RFQ) accelerator, a 7 MeV interdigital H-mode drift tube linac (IH-DTL), and an injection beam transport line. After several stages of beam commissioning, the linac injector has reached a pulsed peak current of 2.5 mA, with normalized emittance (90% particles) less than 4.4 and 2.2 π mm mrad, 90% momentum spread less than ± 0.55%, which lays a good foundation for the beam commissioning of the synchrotron. [ABSTRACT FROM AUTHOR]

Responses of beam position monitors (BPMs) in low-energy beamlines are sensitive to beam velocity and bunching frequency due to non-relativistic effects. However, traditional BPM calibration methods based on the coaxial wire or wire antenna can only simulate electromagnetic fields of high-energy beams with β close to 1. A helix with an inner conductor was adopted to simulate low- β beams. The dispersion relation and characteristic impedance of the helix are analyzed based on the sheath-helix model. The phase velocity and characteristic impedance of the helix have a low dependency on the frequency and helix position inside a BPM, which is crucial for calibrating low- β BPMs. A helix with a phase velocity of 0.12 c and characteristic impedance of 50 Ω is designed to calibrate the button BPMs at the Xi'an Proton Application Facility. Responses of the BPMs to the helix and a beam with β = 0.12 are simulated with CST Studio Suite. The maximum relative calibration error of the helix compared to the beam is 0.47 mm in the transverse positions within three-quarters of the BPM aperture, which shows the remarkable capability of the helix to calibrate low- β BPMs offline. [ABSTRACT FROM AUTHOR]

Knowledge of 4D beam phase space is essential to characterize beam motion along a beamline which includes elements that couple the transverse planes. A 4D phase space measurement method using multiple 2D profiles is proposed in this paper. The effectiveness of the method is validated by numerical simulations. Finally, we present a successful application of the method at the Xi'an Proton Application Facility to measure the coupled 4D phase space after a skew quadrupole. [ABSTRACT FROM AUTHOR]

The experiments of the 0.18-μm pinned photodiode (PPD) CMOS image sensors (CISs) irradiated by energetic proton radiation with energies of 20, 40, 60, and 100 MeV are presented. The degradations of the mean dark signal, dark signal non-uniformity (DSNU), and fixed pattern noise (FPN) induced by protons are presented. The experimental results show that the mean dark signal degradations of the CISs decrease with increasing proton energy at the same fluence. The degradations induced by proton radiation at different fluence are also presented. The mean dark signals increase with increasing integration time at the same proton fluence. The degradation mechanisms of the CISs induced by energetic protons are analyzed. [ABSTRACT FROM AUTHOR]

A new method of measuring the integrated gradient of quadrupoles using a Hall probe is described. The proposed method is developed to measure a Halbach-type permanent magnet quadrupole (PMQ), whose roll angle is difficult to determine for alignment in the measurement. In the proposed method, we establish a roll angle alignment for the magnet, Hall probe, and motor stage based on the field distribution. The proposed method is analyzed and experimentally verified, and a setup is built. Measurement results have confirmed its feasibility for measuring the integrated gradient of PMQs with favorable reproducibility. This method is also an optional method for measuring the integrated gradient of electromagnets. [ABSTRACT FROM AUTHOR]

Abstract Bunch length and momentum spread are two crucial parameters in proton and ion linacs. A non-destructive model-independent rms bunch length and momentum spread measurement method that uses button BPMs is presented in this paper. By using the exponential relation between BPM signal amplitude and rms bunch length, as well as the linear relation between rms bunch length and drift time, rms bunch length and rms momentum spread are derived from several BPMs (three at least) located along the beam line. The effects of beam displacement, beam size, and BPM quantity on the measurement are analyzed. The rms bunch length and the rms momentum spread of the 3-MeV proton beam at the Compact Pulsed Hadron Source (CPHS) of Tsinghua University were successfully measured using this method. The measured rms momentum spread 0.54% is consistent with the simulation value. In addition, the resolution for the rms bunch length and the rms momentum spread measurements were ± 0.017 ns and ± 0.016%, respectively. [ABSTRACT FROM AUTHOR]

A fiducialization method based on vibrating wire is described dedicated to the problem of locating the magnetic center relative to external fiducials for the small-aperture quadrupoles. The advantage of this method is that the measurement of the wire position, which may be the main error source, is no longer needed. The position of the magnetic center can be directly obtained by measuring the position shift of the magnet fiducials. This method has been validated on small Permanent Magnet Quadrupoles (PMQs). Experiments have confirmed its feasibility of measuring PMQs with good repeatability of about 10 μm, and shown its high sensitivity as well as convenience. [ABSTRACT FROM AUTHOR]