A. Schnase

COSY-SCL, the superconducting injector linac for COSY

The superconducting injector linac COSY-SCL is being designed and constructed at the Forschungszentrum Juelich. The train goal of the new injector is to fill the cooler synchrotron COSY with polarized protons as well as with polarized deuterons up to the space-charge limit at injection energy. COSY-SCL is characterized by a base frequency of 160 MHz, 25 kV ion-source extraction voltage, a pulse length of up to 500 /spl mu/s, a maximum repetition rate of 2 Hz, injection into the linac at /spl beta/=0.073 and injection into COSY at kinetic energies of 52 MeV for protons and 56 MeV for deuterons, respectively. The injector configuration is presented, and its main subsystems-ion source (CIPIOS from IUCF for polarized H/sup -/ and D/sup -/), RFQ (built in co-operation with the University of Frankfurt), linac (based on half-wave resonators operating at 160 and 320 MHz)- are described and discussed. The present status of the project is reported.

Cooler synchrotron COSY

Abstract COSY Julich is a cooler synchrotron and storage ring delivering high precision beams with at present up to 5·10 10 protons with momenta between 600 MeV/c and 3.3 GeV/c for medium energy physics. Two cooling systems are used to accomplish this goal. An electron-cooling system that reaches up to a momentum of 645 MeV/c and a stochastic cooling system that covers the upper momentum range from 1500 to 3300 MeV/c. Since its inauguration in April 1993 substantial progress in developing beams for internal and external experiments has been achieved and the physics program is now running. At the beginning of 1996 a polarized proton beam could be successfully accelerated up to 820 MeV/c for the first time.

Acceleration of Polarized Protons and Deuterons at COSY

At the cooler synchrotron COSY, protons and deuterons are accelerated up to 3.65 GeV/c. Vertically polarized proton beams with more than 70% polarization have been delivered in recent years to internal as well as to external experiment areas at different momenta up to the maximum momentum of COSY. In a strong‐focusing synchrotron like COSY, imperfection and intrinsic resonances cause polarization losses during acceleration. The existing magnet system of COSY allows to overcome all imperfection resonances by exciting adiabatic spin flips without polarization losses. A tune‐jump system consisting of two fast quadrupoles has been developed to handle intrinsic resonances in COSY. This magnet system is being successfully utilized at all intrinsic resonances in the momentum range of COSY. For the acceleration of vertically polarized deuterons, additional correction provisions are not necessary to preserve polarization during acceleration because depolarizing resonances are not crossed in the momentum range of C...

Unexpected enhancements and reductions of rf spin resonance strengths

1098-4402= We recently analyzed all available data on spin-flipping stored beams of polarized protons, electrons, and deuterons. Fitting the modified Froissart-Stora equation to the measured polarization data after crossing an rf-induced spin resonance, we found 10–20-fold deviations from the depolarizing resonance strength equations used for many years. The polarization was typically manipulated by linearly sweeping the frequency of an rf dipole or rf solenoid through an rf-induced spin resonance; spin-flip efficiencies of up to 99:9% were obtained. The Lorentz invariance of an rf dipole’s transverse R Bdl and the weak energy dependence of its spin resonance strength E together imply that even a small rf dipole should allow efficient spin flipping in 100 GeVor even TeV storage rings; thus, it is important to understand these large deviations. Therefore, we recently studied the resonance strength deviations experimentally by varying the size and vertical betatron tune of a 2:1 GeV=c polarized proton beam stored in COSY. We found no dependence of E on beam size, but we did find almost 100-fold enhancements when the rf spin resonance was near an intrinsic spin resonance.

The cooler synchrotron COSY in Jülich

Abstract COSY Julich is a cooler synchrotron and storage ring with a proton momentum range from 270 to 3300 MeV/c. It has been conceived to deliver high precision beams for medium energy physics. To accomplish this goal two cooling systems are foreseen: an electron cooling system for the momentum range up to 645 MeV/c and a stochastic cooling system which covers the upper momentum range from 1500 to 3300 MeV/c. Proton beams in a wide momentum range have been delivered to internal as well as external experiments. The beam properties measured by these experiments and the main parameters of COSY are presented.

Design considerations for the linac system of the ESS

Abstract The proposed European spallation neutron source (ESS) will be the leading neutron scattering research facility based on pulsed high intensity/high energy proton beams. According to the present reference design, a linear accelerator produces 1.2 ms long H − beam pulses of 1.334 GeV with a repetition rate of 50 Hz. The beam is accumulated in two rings. The stored beams are extracted in one turn resulting in a pulse of 1.3 μs duration which is delivered to one of the two liquid mercury target stations. Beams from two H − ion sources are pre-accelerated by radio frequency quadrupoles (RFQs), then combined to one beam of about 120 mA. After acceleration in a drift tube linac (DTL) to 70 MeV a coupled cavity linac (CCL) accelerates the beam to the final energy. The CCL can be realized in normal conducting or in superconducting (SC) version which is expected to result in a significant cost reduction for investment and operation.

The RFQ-injector for COSY-SCL

For the new sc-linac for COSY at FZ Julich, a combination of an RFQ and a spiral loaded cavity will accelerate H-, D- beams up to 2.5 MeV/u for injection into the sc-linac. The RFQ is a 3.8 m long four-rod design which accelerates deuterons with an initial energy of 25 keV/u up to 2 MeV/u. Behind the RFQ a compact booster cavity of 300 mm length is mounted. This spiral loaded cavity accelerates the beam to a final energy of 2.5 MeV/u. It uses four accelerating gaps with an effective voltage of 1 MV. An alternative design has gaps with additional electrodes in an RF-quadrupole configuration to add a focussing field in this DTL structure. The status of the work on this new injector is presented.

Overcoming Depolarizing Resonances at COSY

At the cooler synchrotron COSY, polarized protons and deuterons are accelerated up to 3.65 GeV/c. In a strong‐focusing synchrotron like COSY, imperfection and intrinsic resonances cause polarization losses during acceleration. During the acceleration of polarized protons, five imperfection resonances are crossed. The existing magnet system of COSY allows to overcome all imperfection resonances by exciting adiabatic spin flips without polarization losses. The number of intrinsic resonances depends on the superperiodicity of the lattice. A tune‐jump system consisting of two fast quadrupoles has been developed to handle intrinsic resonances in COSY. Vertically polarized proton beams with more than 75% polarization have been delivered in recent years to internal as well as to external experiment areas at different momenta up to the maximum momentum of COSY. For the acceleration of polarized deuterons, additional correction provisions are not necessary to preserve polarization during acceleration. In this pape...

Status of the cooler synchrotron Cosy-Juelich

The cooler synchrotron COSY delivers unpolarized and polarized protons and deuterons in the momentum range 300 MeV/c up to 3.65 GeV/c. Electron cooling at injection level and stochastic cooling covering the range from 1.5 GeV/c up to maximum momentum are available to prepare high precision beams for internal as well as external experiments in hadron physics. The beam is fed to external experiments by a fast kicker extraction or by stochastic extraction. Results of extracted electron cooled beams and developments to increase the number of stored particles and to increase the degree of polarization during acceleration are reported

Beam shaping using a new digital noise generator

A novel digital RF-noise generator was used to excite the COSY-beam longitudinally at a certain harmonic of the revolution frequency. Rectangular shaped noise spectra with bandwidths of the order of 10 kHz and frequency resolution of about 6 Hz were used. Beam distributions were measured during shaping and after switching off the noise source in dependence of bandwidth and amplitude of the RF-noise.