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A 400-MHz niobium quadrupole resonator has been manufactured to study the rf properties of superconducting bulk and thin film samples at low temperatures. We describe the apparatus, i.e., the construction of the resonator, field calculations with MAFIA, and the experimental procedure. In first validation tests the surface resistance R[SUBs] of a reactor-grade bulk niobium sample as a function) of temperature and applied rf field has been investigated by using a calorimetric ''rf-dc-compensation'' method. A critical temperature T[SUBc]=9.15±0.02 K, a thermal conductivity 7lambda;(4.2 K)=6.9±0.7 W/mK, a residual resistance R[SUBres]=19.0±0.3 nΩ, and a superconducting energy gap of Δ/k[SUBB]T[SUBc]=1.82±0.01 have been measured. At 4.2 K we achieved a calorimetric detection limit for R[SUBs] of 0.16 nΩ at a peak field of 25 mT. [ABSTRACT FROM AUTHOR]

Copper cavities with a thin niobium film - as used in the large electron positron collider LEP - would be also attractive for future linear colliders, provided the decrease of the Q-value with the accelerating gradient could be reduced. We aim at extracting the important parameters that govern this decrease. The dependence on the RF frequency is studied by exciting 500 MHz and 1500 MHz cavities in different modes. In addition we combined RF measurements for two 1500 MHz cavities of different RF performance with microscopic tests (AFM,TEM) on samples cut out of the same cavities. Their microstructural characterization in plan-view allows the extraction of the grain size and the defect densities. [ABSTRACT FROM PUBLISHER]

CERN's Linac4 45 kV H- ion sources prototypes are installed at a dedicated ion source test stand and in the Linac4 tunnel. The operation of the pulsed hydrogen injection, RF sustained plasma, and pulsed high voltages are described. The first experimental results of two prototypes relying on 2 MHz RF-plasma heating are presented. The plasma is ignited via capacitive coupling, and sustained by inductive coupling. The light emitted from the plasma is collected by viewports pointing to the plasma chamber wall in the middle of the RF solenoid and to the plasma chamber axis. Preliminary measurements of optical emission spectroscopy and photometry of the plasma have been performed. The design of a cesiated ion source is presented. The volume source has produced a 45 keV H- beam of 16-22 mA which has successfully been used for the commissioning of the Low Energy Beam Transport (LEBT), Radio Frequency Quadrupole (RFQ) accelerator, and chopper of Linac4. [ABSTRACT FROM AUTHOR]

CERN's superconducting proton Linac (SPL) study investigates a 50 Hz high-energy, high-power Linac for H- ions. The SPL plasma generator is an evolution of the DESY ion source plasma generator currently operated at CERN's Linac4 test stand. The plasma generator is a step towards a particle source for the SPL, it is designed to handle 100 kW peak RF-power at a 6% duty factor. While the acquisition of an integrated hydrogen plasma optical spectrum is straightforward, the measurement of a time-resolved spectrum requires dedicated amplification schemes. The experimental setup for visible light based on photomultipliers and narrow bandwidth filters and the UV spectrometer setup are described. The Hα, Hβ, and Hγ Balmer line intensities, the Lyman band and alpha transition were measured. A parametric study of the optical emission from the Linac4 ion source and the SPL plasma generator as a function of RF-power and gas pressure is presented. The potential of optical emission spectrometry coupled to RF-power coupling measurements for on-line monitoring of short RF heated hydrogen plasma pulses is discussed. [ABSTRACT FROM AUTHOR]

For the GSI future project Facility for Antiproton and Ion Research a beam intensity of 1012 U28+ions/s is planned to be extracted from the GSI heavy ion synchrotron SIS18. Measurements performed in 2001 showed that the beam lifetime of the ions in the synchrotron is decreasing with increasing number of injected particles due to vacuum instabilities caused by ion-induced desorption. The injection energy for the SIS18 is about 10 MeV/u and U28+ ions are accelerated to 200 MeV/u limited by the magnetic rigidity for the low charge state. The aim of this work was to measure the desorption yield as a function of the impact energy from injection to extraction of SIS18 at GSI. Low energy yields at 5.0, 9.7, and 17.7 MeV/u were measured at the Cyclotron of The Svedberg Laboratory in Uppsala. High energy yields at 40, 80, and 100 MeV/u were measured at SIS18 of GSI in a different setup. It was found that the desorption yield scales with the electronic energy loss (dE/dx)eln, with n between 2 and 3, decreasing for increasing impact energy above the Bragg maximum. [ABSTRACT FROM AUTHOR]