Abstract Ceramic breaks are used in synchrotrons for many purposes. For example, they are inserted between the Multi-Wire Profile Monitor (MWPM) on the injection line at the Rapid Cycling Synchrotron (RCS) in J-PARC to completely prevent the wall currents accompanying beams from affecting the MWPM. On the other hand, from the viewpoint of suppressing beam impedances and the radiation fields from the ceramic breaks, it would be preferable that the inner surface of the ceramic break is coated with Titanium Nitride (TiN), or covered over capacitors. In this report, we measure the radiation fields from the ceramic break with and without capacitors as well as the beam profile and investigate the effect of the ceramic breaks on the measurements.
We have established and also implemented a nondestructive online monitoring system for measuring the stripper foil degradation, such as foil thinning and pinhole outbreak, for the first time during beam operation in a high-intensity proton accelerator. We aimed to achieve a realistic and longer lifetime of a stripper foil by ensuring proper uses and determining its end of usefulness without any failure. A stripper foil is used for negative hydrogen (${\mathrm{H}}^{\ensuremath{-}}$) stripping to proton (p) for multiturn charge-exchange injection in high-intensity proton accelerators. A longer foil lifetime is expected, while foil failure during operation should be avoided, as it reduces the accelerator availability and also has serious issues for regular accelerator maintenance. A proper use of the foil should also be ensured to minimize the replacement of the foil magazine, as it involves unhealthy radiation exposure to the workers. We have measured the partially stripped ${\mathrm{H}}^{0}$ and unstripped ${\mathrm{H}}^{\ensuremath{-}}$ charge fractions of the injection ${\mathrm{H}}^{\ensuremath{-}}$ beam out of the stripper foil to understand details of foil degradation, such as foil thinning and pinhole formation due to high-intensity beam irradiation, which are believed to be foil breaking signals. We used two independent beam monitoring devices and precisely measured both ${\mathrm{H}}^{0}$ and unstripped ${\mathrm{H}}^{\ensuremath{-}}$ charge fractions by each monitor. As a result, we obtained a detail of foil degradation during operation to determine a realistic end of its usefulness by successfully achieving a record of nearly 2 yr of operation with a single foil without any failures. The detailed measurement result of the foil degradation also gives strong feedback for producing stronger and durable stripper foils. The present research was done by using simple and ordinary beam diagnostic devices including a nondestructive one, which can be easily applied to overcome the stripper foil issues in any similar existing and next-generation further higher-intensity accelerators.
We have established an advanced and sophisticated uses of a current transformer and a multi-wire profile monitor for accurate measuring as well as online monitoring of the waste beam so as to know the stripper foil degradation during user operation of the J-PARC 3-GeV RCS. A more than 99.7% of the H beam coming from the Linac is stripped to a proton beam by using an HBC stripper foil of 200 µg/cm 2 placed in the RCS injection area. The remaining 0.3% is called the waste beam and is transported to the injected beam dump. Foil degradation such as, foil thinning and pinhole formation are believed to be the signs of a foil breaking. A sudden foil breaking is not only decreases accelerator availability but also raises maintenance issues. A proper monitoring system of the foil is thus important in order to avoid any such issues by replacing the foil with a new one in the scheduled maintenance day. The sensitivity of the present method has already been proved to be very good and is capable of monitoring a change of the foil thickness as low as 1% or even less. A single foil was used for a continuous last 7 months operation of the RCS with an extracted beam power of 300 kW (18 kW injected beam). The integrated total irradiated particles (injected H itself) were 8 ×10 21 but there was no any degradation of the foil so far. Surprisingly an increase of the foil thickness of about 10% was observed.
The J-PARC MR beam monitor system have been installed and tested at day-one beam commissioning started this May. In this paper, the requirements for the monitor system to achieve high power beam acceleration up to 50 GeV, 0.73MW, andthe present performances are presented.
The Beam Based Alignment (BBA) of the BPM is inevitable for precise and absolute beam position measurements. Even though careful fabrication and installation of the BPM detector, it has to be calibrated by using the beam. Usually, it requires that the individual quadrupole magnet is able to be controlled. However, it is not always that case. In addition, scanning over the all BPM is time consuming procedure. The BBA method under coupled QM environment would help to reduce time for calibration. It presents general formula and experiences at J-PARC RCS and parts of results are compared with the ordinal method at J-PARC MR.
