Does Foreign Aid Improve Governance?

This paper analyses the impact of aid flows on governance. Using an instrumental variable approach and a large country sample, we find that aid has a negative rather than a positive influence on governance. This outcome is robust to various model specifications. --Official Development Assistance,Governance

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

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

Recent Experiments on the Effect of Coherent Synchotron Radiation on the Electron Beam Effect of CTF II

The drive beam of CTF II can provide single electron bunches with charges of more than 15 nC and rms lengths of less than 0.13 mm. If the bunches are bent in the dipoles of a magnetic bunch compressor, they emit coherent synchrotron radiation with strongly enhanced intensity with respect to incoherent synchrotron radiation. Here we report on the experimental and theoretical study of the effect of this coherent radiation emission on the distribution of the electrons in the six-dimensional phase space. Transverse emittances, bunch lengths, and energy spectra were measured for constant bunch compression ratios but different horizontal beam sizes in the bunch compressor. Further, the shielding effect of the finite vacuum chamber height on the mean beam energy loss was investigated by using two vacuum chambers of different heights in a four-magnet chicane. The results are compared with simulations using TraFiC 4 and ELEGAN