A   B   C   D   E   F   G   H   I   K   L   M   O   P   Q   R   S   T   U   V  

cryogenics

Paper Title Other Keywords Page
TUPB12 BPMs for the XFEL Cryo module linac, quadrupole, pick-up, alignment 84
 
  • D. Nölle, N. Baboi, K. Knaack, D. Lipka, J. Lund-Nielsen, N. Mildner, R. Neumann, F. Schmidt-Föhre, M. Siemens, T. Traber, S. Vilcins
    DESY, Hamburg
  The European XFEL is based on superconducting accelerator technology developed in the context of the TESLA collaboration. The accelerator itself consist of cryo modules each equipped with 8 cavities, followed by a quadrupole/steerer package, a BPM and a HOM absorber. This contribution will present the layout of the BPM system for the cryo modules, describing the monitor itself, its integration into the cryo module. Additionally, the electronics concept will be discussed. Finally the results of beam measurements at FLASH using prototypes of the monitor and the electronics will be presented.  
 
TUPB16 Optimization of the Linear-cut Beam Position Monitors Based on Finite Element Methods simulation, coupling, quadrupole, pick-up 96
 
  • P. Kowina, W. Kaufmann, J. Schölles
    GSI, Darmstadt
  This contribution presents simulations of the Beam Position Monitors (BPMs) for the FAIR project that were performed using CST Studio Suite 2006B. The linear-cut BPMs based on a metal-coated ceramics were considered as the only solution that meets the required mechanical stability under cryogenic conditions. The essential BPM features like position sensitivity or linearity of position determination were compared for two geometries. In these geometries, in both cases based on elliptically shaped ceramic pipe, the vertical and horizontal electrode pairs were either mounted subsequently in series or were spirally shaped and combined alternatively within one unit. It is shown that optimization of BPM design increases position sensitivity by more than a factor of two. The frequency dependence of the position sensitivity and an offset of electrical center of BPM in respect to its geometrical center were analyzed in the bandwidth of 200 MHz. In a frequency range up to 100 MHz (i.e. typical for the BPM applications) calculated variations of the displacement sensitivity are smaller than 1%; the careful design of a guard ring configuration allows keeping the offset consistent with zero.  
 
WEPB23 Beam Diagnostics Development for the Cryogenic Storage Ring CSR ion, diagnostics, electron, pick-up 283
 
  • T. Sieber, H. Fadil, M. Grieser, A. Wolf, R. von Hahn
    MPI-K, Heidelberg
  A cryogenic storage ring is under construction at the MPI-K Heidelberg. It consists of electrostatic elements and has a circumference of ~35m. The CSR shall be used for storage of rotationally non-excited molecules and highly charged ions, therefore extremely low temperatures (<4K) and gas pressures (10-15 mbar) are required. The ring shall also be operational at room temperature and bakeable to at least 300°C. The maximum energy of singly charged ions is 300keV, intensities will be in the range 1nA – 1uA. For the mass range, A<100 is taken as reasonable design value, in later stages of CSR operation experiments with heavier ions are foreseen. Due to the exceptional boundary conditions we are working on new or further developments for most of the diagnostics devices. For example our RGMs have to produce their own local pressure bumps. The MCPs have to work at temperatures around 4K. The beam position pickups shall be operated in resonant mode for increased sensitivity. Our beam profiler will use secondary electrons from a stopper plate, which allows beam imaging in the intensity range 102 to 1012 pps. For intensity measurements a SQUID CCC system is under discussion.  
 
WEPB30 Current Status of the SQUID Based Cryogenic Current Comparator for Absolute Measurements of the Dark Current of Superconducting RF Accelerator Cavities pick-up, electron, shielding, controls 301
 
  • K. Knaack, K. Wittenburg
    DESY, Hamburg
  • R. Neubert, S. Nietzsche, F. Schiller, W. Vodel
    FSU Jena, Jena
  • A. Peters
    HIT, Heidelberg
  This contribution gives an overview on the current status of a LTS-SQUID based Cryogenic Current Comparator (CCC) for detecting dark currents, generated for example by superconducting cavities for the upcoming X-FEL project. To achieve the maximum possible energy the gradients of the superconducting RF accelerator cavities should be pushed close to the physical limit of 50 MV/m. The so-called dark current of the superconducting RF cavities at strong electric fields may limit the maximum gradient. The absolute measurement of the dark current in correlation with the gradient will give a proper value classify the cavities. The main component of the CCC is a LTS-DC SQUID system which allows us to measure extremely low magnetic fields, caused by extracted dark currents of RF cavities under test. For this reason the SQUID input coil is connected across a toroidal superconducting pick-up coil (inner diameter: about 100 mm) for the passing electron beam. A noise limited current resolution of 40 pA/sqrt(Hz) with a measurement bandwidth of up to 70 kHz was achieved. Design issues and the application for the CHECHIA cavity test stand at DESY as well as experimental results will be discussed.