RF empty bucket channelling combined with a betatron core to improve slow extraction in medical synchrotrons

The uniformity of a slow-extracted beam from a synchrotron is degraded by ripples from the power converters of the magnetic elements. This effect can be reduced by making the beam particles cross more quickly from the stable to the unstable region. Among the various methods that have been proposed for this purpose, RF bucket channelling seems to be a good candidate for compensating low frequency ripples in spills of the order of one second. The method is based on the technique of RF phase displacement acceleration. In the configuration studied, a coasting beam is accelerated slowly into a third-order resonance by a betatron core. The acceleration rate set by the betatron core determines the spill length. Empty buckets are then created at the resonance frequency and adjusted with a phase angle that would decelerate any trapped beam by an equal and opposite amount. The main RF system can be used for this purpose. The empty buckets cause an obstruction in phase space and the beam particles are forced to channel around the buckets. The particle speed is thus increased as the particle crosses into the resonance region, making the extraction less sensitive to ripple. The energy at which the particles enter in the unstable region is not fixed, but depends on their momentum and betatron amplitude. An improvement factor is obtained for all momenta and betatron amplitudes, provided that the bucket is properly positioned and that its half height is greater than the energy spread engaged in the resonance. The existing theory is extended to show that particles entering at different energies get different improvement factors, and how the improvement in the spill depends on the frequency and amplitude of the ripple

Improved meteorological measurements from buoys and ships (IMET) : preliminary comparison of precipitation sensors

Rainfall data obtained from an optical rain gauge and a capacitive siphon rain gauge are analyzed and discussed. These sensors were developed for unattended use and are being considered for use at sea on ships and buoys.Funding was provided by the National Science Foundation under Grant No. OCE-87-0961

The RF Cycle of the PIMMS Synchrotron

This paper deals with the study of the rf cycle of the synchrotron of the Proton-Ion Medical Machine Study (PIMMS) hosted at CERN. The cycle comprises the adiabatic trapping, the acceleration and the rf gymnastics, both for protons and fully stripped carbon ions. The injection energy is 20 MeV for protons and 7 MeV/u for carbon. The maximum extraction energies are 250 MeV for protons and 400 MeV/u for carbon ions. The reserved time is less than 1 s, with a maximum magnetic field ramp of less than 3 T/s. The simulations show that the beam stays inside the aperture of the machine, and that there are no longitudinal losses. At the end of the cycle the beam is ready for extraction with a Dp/p of 0.4 %. The peak rf voltage is 3 kV and the frequency range is from 0.49 to 2.85 MHz

The RF Cycle of the PIMMS Medical Synchrotron

This paper presents the design of the RF cycle of the medical synchrotron of the PIMMS (Proton-Ion Medical Machine Study) hosted at CERN. The cycle comprises adiabatic trapping, acceleration and RF gymnastics, for either protons or fully stripped carbon ions. The injection energy is 20 MeV for protons and 7 MeV/u for carbon. Maximum extraction energies are 250 MeV for protons and 400 MeV/u for carbon ions. The cycle duration is less than 1 s, with a maximum magnetic field ramp below 3 T/s. The simulations show that the beam stays inside the aperture of the machine, and that, theoretically, there are no longitudinal losses. At the end of the cycle, the beam is ready for extraction with a Dp/p = 0.4 %. The peak RF voltage is 3 kV and the frequency ranges from 0.4 to 3 MHz

A Single Pulse Beam Emittance Measurement for the CERN Heavy Ion Linac

A new device for transverse emittance measurement has been installed in the 4.2 MeV/u filter region of the CERN Heavy Ion Linac (Linac 3). It allows to obtain pulse-to-pulse (every 1.2 sec) visualisation of the Linac 3 beam parameters in order to tune the machine and to match the beam for injection into the first circular accelerator, the PS Booster. The system is based on the "multi-slit" technique similar to the well-known "pepper pot" method. A plate with a series of horizontal or vertical slits is placed in the beam, defining positions in the phase plane. Particles pass through the slits and drift to a scintillator screen where they produce light. The screen is looked at by an externally triggered high resolution CCD camera. For each slit position the light intensity distribution, in the limit of infinitesimal slit aperture, is proportional to the angle distribution of the particles and therefore, provides the angular distribution in the phase plane. The video signal from the camera is digitised and the result stored in a 512 x 512 x 8 frame store. An application program visualising slit images (raw data) as well as the calculated emittance ellipses has been developed. This program also delivers numerical values for the rms-emittance and the Twiss parameters. The paper discusses the method, the prototype realisation, the data treatment and first experimental results obtained during the running-in of Linac 3

Improved meteorological measurements from buoys and ships (IMET) : preliminary report on barometric pressure sensors

Stability tests over periods ranging from 3 to 19 months have been carried out on Paroscientific models 215-AT and 760-15A, AIR DB-1A, Rosemount 1201F1B, Setra 270 and Heise 623 electronic barometers. The Paroscientific barometers had the highest accuracy, stability, and price, and the lowest power consumption. The Rosemount 1201FIB had excellent stability but high power consumption as well as price. The AIR DB-1A and Setra 270 have good stability and moderate power consumption and price. The tests are being expanded to include inexpensive sensors.Funding was provided by the National Science Foundation under Grant No. OCE-87-0961

Improved meteorological measurements from buoys and ships (IMET) : preliminary comparison of solar radiation air temperature shields

Several different types of solar radiation air temperature shields are evaluated for use at sea on ships and buoys. They include three types of static or Thaller shields, two vane oriented shields, and two fan ventilated shields. A preliminary data analysis is presented and discussed.Funding was provided by the National Science Foundation under Grant No. OCE-87-0961

Improved meteorological measurements from buoys and ships (IMET) : preliminary comparison of humidity sensors

Humidity sensors using various principles of operation are evaluated for the potential use at sea on buoys and ships. Thin film capacitive polymer sensors include the Vaisala Humicap HMP-14U (with WHOI electronics), Hy-Cal Engineerig Ultra-H (also with WHOI electronics), the new Vaisala HMP-35A, and the Rotronic MP-lOOF. Impedance sensors include the Thunder Scientific PC-2101, Phys-Chem PCRC-ll, and the General Eastern 850. The Hygrometrix 8503A is the only organically based cellulose crystallite sensor evaluated. Chilled mirror dew sensors include the EG&G 200M Dewtrak, which was used as a comparative standard, the General Eastern Dew-lO and the WHOI D10IQ Intelligent Dew Point Sensor. The IR-200 infrared optical hygrometer from Ophir is also included in this study. The performance of the EG&G 200M Dewtrak was quite disappointing. Errors of up to 2.5°C in air temperature were observed due to inadequate shielding from solar radiation.Funding was provided by the National Science Foundation under Grant No. OCE-87-09614