First Results of Magnetic Field Penetration Measurements of Multilayer SIS Structures

The performance of superconducting RF cavities made of bulk Nb is limited by a breakdown field of Bp ≈200 mT, close to the superheating field for Nb. A potentially promising solution to enhance the breakdown field of the SRF cavities beyond the intrinsic limits of Nb is a multilayer coating suggested in [1]. In the simplest case, such a multilayer may be a superconductor-insulator-superconductor (S-I-S) coating, for example, bulk niobium (S) coated with a thin film of insulator (I) followed by a thin layer of another superconductor (S) which could be e.g. dirty niobium [2]. Here we report the first results of our measurements of field penetration in Nb thin films and Nb-AlN-Nb multilayer samples at 4.2 K using the magnetic field penetration facility designed, built and tested in ASTeC

Physical vapour deposition of NbTiN thin films for superconducting RF cavities.

The production of superconducting coatings for radio frequency (RF) cavities is a rapidly developing field that should ultimately lead to acceleration gradients greater than those obtained by bulk Nb RF cavities. The use of thin films made from superconductors with thermodynamic critical field, Hc > HC(Nb), allows the possibility of multilayer superconductor – insulator – superconductor (SIS) films and accelerators that could operate at temperatures above 2 K. SIS films theoretically allow increased acceleration gradient due to magnetic shielding of underlying superconducting layers [1] and higher operating temperature can reduce cost [2]. High impulse magnetron sputtering (HiPIMS) and pulsed DC magnetron sputtering processes were used to deposit NbTiN thin films onto Si(100) substrate. The films were characterised using scanning electron microscopy (SEM), x-ray diffraction (XRD), Rutherford back-scattering spectroscopy (RBS) and a four-point probe

Conceptual design of a nonscaling fixed field alternating gradient accelerator for protons and carbon ions for charged particle therapy

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.The conceptual design for a nonscaling fixed field alternating gradient accelerator suitable for charged particle therapy (the use of protons and other light ions to treat some forms of cancer) is described.EPSR

High intensity neutrino oscillation facilities in Europe

The EUROnu project has studied three possible options for future, high intensity neutrino oscillation facilities in Europe. The first is a Super Beam, in which the neutrinos come from the decay of pions created by bombarding targets with a 4 MW proton beam from the CERN High Power Superconducting Proton Linac. The far detector for this facility is the 500 kt MEMPHYS water Cherenkov, located in the Fréjus tunnel. The second facility is the Neutrino Factory, in which the neutrinos come from the decay of μ+ and μ− beams in a storage ring. The far detector in this case is a 100 kt magnetized iron neutrino detector at a baseline of 2000 km. The third option is a Beta Beam, in which the neutrinos come from the decay of beta emitting isotopes, in particular He6 and Ne18, also stored in a ring. The far detector is also the MEMPHYS detector in the Fréjus tunnel. EUROnu has undertaken conceptual designs of these facilities and studied the performance of the detectors. Based on this, it has determined the physics reach of each facility, in particular for the measurement of CP violation in the lepton sector, and estimated the cost of construction. These have demonstrated that the best facility to build is the Neutrino Factory. However, if a powerful proton driver is constructed for another purpose or if the MEMPHYS detector is built for astroparticle physics, the Super Beam also becomes very attractive

REALISATION OF A PROTOTYPE SUPERCONDUCTING CW CAVITY AND CRYOMODULE FOR ENERGY RECOVERY

Abstract For Energy Recovery applications, the requirement for high-Q accelerating structures, operating in CW mode, at large beam currents, with precise phase & amplitude stability and modest accelerating gradients are all fundamental in achieving intense photon fluxes from the synchronised FEL insertion devices. Both Daresbury Laboratory and Cornell University are developing designs for advanced Energy Recovery Linac (ERL) facilities which require accelerating Linacs which meet such demanding criteria. The specification for the main ERL accelerator for both facilities dictates a modest accelerating gradient of 20 MV/m, at a Q o of better than 10 10 , with a Q ext of up to 10 8 . A collaborative R&D program has been set-up to design and fabricate a 'proofof-principle' cryomodule (which is well underway) that can be tested on ERLP at Daresbury and also on the Cornell ERL injector. This paper details the new cryomodule design, provides an insight to the design solutions employed and reports on the present status of the project

RECENT DEVELOPMENTS ON ALICE (ACCELERATORS AND LASERS IN COMBINED EXPERIMENTS) AT DARESBURY LABORATORY

Abstract Progress made in ALICE (Accelerators and Lasers In Combined Experiments) commissioning and a summary of the latest experimental results are presented in this paper. After an extensive work on beam loading effects in SC RF booster and linac cavities' conditioning, ALICE can now operate in full energy recovery mode at a bunch charge of 40pC, a beam energy of 27.5MeV and train lengths of up to 100µs. This improved operation of the machine has resulted in generation of coherentlyenhanced broadband terahertz radiation with an energy of several tens of microjoules per pulse and in successful demonstration of the Compton Back-Scattering x-ray source experiment. Experiments on the exposure of living cells to terahertz radiation have been started. These and other developments on ALICE are reported. MACHINE STATUS ALICE, an energy-recovery superconducting linac GaAs photocathode lifetime is now sufficiently long for routine ALICE operation at 40pC. Normally cathode recaesiation is performed once a month, when the quantum efficiency decreases from initial ~3% to below ~0.5%. Over the past year, a number of changes in gradient settings of SC cavities (booster and main linac) were made with the aim of optimising the RF set up and to accommodate limitations presented by the RF system. Each of these variations required significant changes in the overall machine set up. It can now be routinely operated at 27.5MeV with the total beam losses not exceeding 5 to 7%. The energy spectrum of the beam exiting the first cavity of the booster (BC1) with the second cavity (BC2) switched off (resulting in a beam energy of 3.9MeV, compared to the nominal injector energy of 6.5MeV) is shown i