The polarimetry chain for the P2 experiment

We plan to equip the P2 experiment at Mainz with two different types of polarimeters, a so-called double scattering Mott polarimeter and a Møller polarimeter with trapped polarized hydrogen atoms (Hydro-Møller polarimeter). We believe that both polarimeters have the potential to achieve an accuracy in the determination of the effective analyzing power of less than 0.5%

A method to polarise antiprotons in storage rings and create polarised antineutrons

An intense circularely polarised photon beam interacts with a cooled antiproton beam in a storage ring. Due to spin dependent absorption cross sections for the reaction gamma+antiproton > pi- + antineutron a built-up of polarisation of the stored antiprotons takes place. Figures-of-merit around 0.1 can be reached in principle over a wide range of antiproton energies. In this process antineutrons with Polarisation > 70% emerge. The method is presented for the case of 300 MeV/c cooled antiproton beam

A surprising method for polarising antiprotons

We propose a method for polarising antiprotons in a storage ring by means of a polarised positron beam moving parallel to the antiprotons. If the relative velocity is adjusted to $v/c \approx 0.002$ the cross section for spin-flip is as large as about $2 \cdot 10^{13}$ barn as shown by new QED-calculations of the triple spin-cross sections. Two possibilities for providing a positron source with sufficient flux density are presented. A polarised positron beam with a polarisation of 0.70 and a flux density of approximately $1.5 \cdot 10^{10}$/(mm$^2$ s) appears to be feasible by means of a radioactive $^{11}$C dc-source. A more involved proposal is the production of polarised positrons by pair production with circularly polarised photons. It yields a polarisation of 0.76 and requires the injection into a small storage ring. Such polariser sources can be used at low (100 MeV) as well as at high (1 GeV) energy storage rings providing a time of about one hour for polarisation build-up of about $10^{10}$ antiprotons to a polarisation of about 0.18. A comparison with other proposals show a gain in the figure-of-merit by a factor of about ten.Comment: 13 pages, 8 figures; v2: minor language and signification corrections v3: (14 pages, 12 figures) major error, nonapplicable polarisation transfer cross sections replaced by the mandatory spin-flip cross section

Initial test of an rf gun with a GaAs cathode installed

The operation of an rf gun with a GaAs crystal installed as the cathode has been tested in anticipation of eventually producing a polarized electron beam for a future e{sup +}/e{sup -} collider using an rf photoinjector

Bunch Compressor Performances at the CLIC Test Facility

The Test Facility of the "Compact Linear Collider" (CLIC) at CERN (CTF), has to prove the feasibility of transporting high charge beams through decelerating structures at 30 GHz to create RF power. This RF power is used to supply, in the final scheme, the cavities of the main linac. To optimise this power generation, a bunch compressor has been installed in the test line. This compressor shortens the electron bunches after creation and acceleration in the RF gun. The compressed bunches are then accelerated by a high gradient cavity (50 MV/m) and transported to a 30 GHz cavity. Compressed bunch length mesurements showed that lengths of 0.6 mm (rms) were obtained at the entrance of 30 GHz cavity for a 10 nC beam. Compression of electron bunches of charges between 2 and 17 nC have also been measured. Emittance measurements were done to study the transverse effects of the bunch compressor on the beam. The use of the code PARMELA allowed the design and optimisation of the chicane. The simulations results have been compared to the experimental measurements

Further R&D For A New Superconducting Cw Heavy Ion Linac@GSI

A low energy beam line (1.4 MeV/u) behind the GSI High Charge State Injector (HLI) will provide cw-heavy ion beams with high beam intensity. It is foreseen to build a new cw-heavy ion LINAC for post acceleration up to 7.3 MeV/u. In preparation an advanced R&D program isdefined: The first LINAC section (financed by HIM andpartly by HGF-ARD-initiative) comprising a sc CH-cavity embedded by two sc solenoids will be tested in2014/15 as a demonstrator. After successful testing theconstruction of an advanced cryo module comprising fourCH cavities is foreseen. As an intermediate step towardsan entire cw-LINAC the use of a double of two CH-cavities is planned: A short 5 cell cavity should bemounted directly behind the demonstrator cavity inside ashort cryostat. The design of the cw LINAC based onshorter sc CH-cavities would minimize the overalltechnical risk and costs. Besides with this cavity anoptimized operation of the whole LINAC especially withrespect to beam quality could be achieved. Last but notleast the concept of continuous energy variation applyingphase variation between the two cavities with constantbeta profile could be tested

First attempt of the measurement of the beam polarization at an accelerator with the optical electron polarimeter POLO

The conventional methods for measuring the polarization of electron beams are either time consuming, invasive or accurate only to a few percent. We developed a method to measure electron beam polarization by observing the light emitted by argon atoms following their excitation by the impact of polarized electrons. The degree of circular polarization of the emitted fluorescence is directly related to the electron polarization. We tested the polarimeter on a test GaAs source available at the MAMI electron accelerator in Mainz, Germany. The polarimeter determines the polarization of a 50 keV electron beam decelerated to a few eV and interacting with an effusive argon gas jet. The resulting decay of the excited states produces the emission of a circularly polarized radiation line at 811.5 nm which is observed and analyzed