High power test of a 30 GHz planar accelerator

A 30-GHz muffin-tin, traveling-wave accelerating structure consisting of 37 cells was tested at high power using the CTF2 at CERN. The structure was fabricated with conventional milling and brazing, including tuning holes at cavity roofs. No special surface preparation or treatment was done to the structure. A maximum peak power in excess of 100 MW at a pulse width of 4 ns was transported through the structure before electron bursts were initiated. A maximum accelerating gradient of 60 MV/m was achieved with a peak RF power of 40 MW at a pulse width of 8 ns

Status of CLIC High-gradient Studies

The recent RF structure testing program carried out in the CLIC Test Facility, CTF II, is described. The main objectives of the testing program have been to gain an insight into the physical processes involved in breakdown and damage, to isolate parameters that influence breakdown and damage, and to determine gradient limits for 30 GHz structures. The layout of CTFII in the new 'Test Stand' configuration, the instrumentation used to study breakdown and the experimental results are summarised. The new results are compared to previously published results at 11, 30 and 33 GHz produced in the context of the CLIC study

Transplantation of progenitor cells and regeneration enhancement in acute myocardial infarction - (TOPCARE-AMI)

Background - Experimental studies suggest that transplantation of blood-derived or bone marrow–derived progenitor cells beneficially affects postinfarction remodeling. The safety and feasibility of autologous progenitor cell transplantation in patients with ischemic heart disease is unknown

A 30 GHz beam driven high gradient single cell cavity test

In December 1999 a first 30 GHz high gradient experiment [1] was performed using a single cell excited directly by the high-charge drive beam of the CLIC Test Facility (CTF II) [2]. Since this experiment showed quite promising results (peak surface fields of 300 MV/m were measured) it was decided to remeasure the cavity with improved vacuum, diagnostics and data acquisition. In addition an experiment was prepared to cool the cavity with liquid nitrogen and heat it with a hot air gun. The electrical breakdown behaviour was measured as a function of the cavity temperature. The breakdown threshold was found to be at a maximum surface field of 380 MV/m and remained unchanged in the accessible temperature range between 100 K to 500 K. Large data samples were taken to provide statistics of unforseen delays and frequency shifts that occur during breakdown event

High power testing of 30 GHz accelerating structures at the Clic Test Facility (CTF II)

During the year 2000, experiments using the CLIC Test Facility [1] (CTF II) focused on high-power testing of 30 GHz CLIC prototype accelerating structures [2] (CAS) and on investigating the processes involved in RF breakdown. For this purpose, a 30 GHz high-power test stand equipped with diagnostics for breakdown studies has been developed. The experimental set-up, diagnostics and performance of the one meter long power extraction structure used to feed the accelerating structures with 30 GHz power will be described. A single-feed coupler CAS assembled by AEG, a planar structure produced by the University of Berlin, and a double-feed coupler CAS made at CERN, were tested in CTF. The accelerating and surface gradient limits found for these structures at different RF pulse lengths, and ideas about the processes involved in electrical breakdown, are summarised and discussed

CLIC High-Gradient Test Results

The CLIC (Compact Linear Collider) high-gradient RF structure testing program has been carried out in order to gain insight into the physical processes involved in RF breakdown, determine the mechanisms that limit gradient and produce damage so that technical concepts can be developed which allow higher accelerating gradients. Two main paths towards higher gradients have emerged from this program, and the performances of two new structures which incorporate them are presented

30 GHz RF Pulse Stretcher for CTF2

A 30 GHz pulse stretcher was designed, manufactured, tuned, and installed within a period of about two months and was successfully used in CTF2 to investigate the pulse length dependence of maximum achievable surface gradient in one of the copper 30 GHz accelerating structures

Time resolved spectrometry on the CLIC Test Facility 3

The high charge (>6ìC) electron beam produced in the CLIC Test Facility 3 (CTF3) is accelerated in fully beam loaded cavities. To be able to measure the resulting strong transient effects, the time evolution of the beam energy and its energy spread must be determined with at least 50MHz bandwidth. Three spectrometer lines are installed along the linac in order to control and tune the beam. The electrons are deflected by dipole magnets onto Optical Transition Radiation (OTR) screens which are observed by CCD cameras. The measured horizontal beam size is then directly related to the energy spread. In order to provide time-resolved energy spectra, a fraction of the OTR photons is sent onto a multi-channel photomultiplier. The overall setup is described, special focus is given to the design of the OTR screen with its synchrotron radiation shielding. The performance of the time-resolved measurements are discussed in detail. Finally, the limitations of the system, mainly due to radiation problems are discussed

Laser Wire Scanner Development on CTF II

A laser wire scanner is under development at CERN in the framework of the Compact Linear Collider study (CLIC). A first test has been carried out at the CLIC Test Facility II (CTF II) with the aim of developing a beam profile monitor for a low energy, high charge electron beam. In our set-up a 2.5 mJ, 1047 nm, 4 ps laser pulse interacts with a 50 MeV, 1 nC, 4 ps electron bunch. A scintillator detects up to 600 X-ray photons, with an average energy of 17 keV. In the present status of the experiment Thomson photons have been observed, but the signal to noise ratio is however still too low for an accurate profile measurement