[PISA - Reaktionen der teilnehmenden Länder Juli-Oktober 2002] Niederlande. Zusammengestellt nach Pressemitteilungen des Bildungsministeriums und Berichten der niederländischen Presse

Die folgende kurze Übersicht über die Rezeption der PISA-Studie in den Niederlanden basiert vor allem auf Presseberichten und Pressemitteilungen des Bildungsministeriums. Nicht nur in der Presse hat die PISA-Studie Diskussionen ausgelöst. Auch im niederländischen Schulleiterverein (VVO) wurde die PISA-Studie diskutiert. Derzeit wird durch den Schulleiterverein eine Umfrage unter niederländischen Schulleitern organisiert, deren Ziel es ist, zu ermitteln, wie sich die niederländischen Schulleiter die nicht ausreichende Teilnahme der Schulen und Schüler an der PISA-Studie sowie die bei einer internen Auswertung der vorliegenden Stichprobe erzielten guten Resultate erklären. (DIPF/Orig.

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

Beam dynamics studies and emittance optimization in the CTF3 linac at CERN

Small transverse beam emittances and well-known lattice functions are crucial for the 30 GHz power production in the Power Extraction and Transfer Structure (PETS) and for the commissioning of the Delay Loop of the CLIC Test Facility 3 (CTF3). Following beam dynamics simulation results, two additional solenoids were installed in the CTF3 injector in order to improve the emittance. During the runs in 2005 and 2006, an intensive measurement campaign to determine Twiss parameters and beam sizes was launched. The results obtained by means of quadrupole scans for different modes of operation suggest emittances well below the nominal .n,rms = 100 ?Î?Êm and a good agreement with PARMELA simulations

Efficient long-pulse fully-loaded CTF3 linac operation

An efficient RF to beam energy transfer in the accelerating structures of the drive beam is one of the key points of the Compact Linear Collider (CLIC) RF power source. For this, the structures are fully beam-loaded, i.e. the accelerating gradient is nearly zero at the downstream end of each structure. In this way, about 96 % of the RF energy can be transferred to the beam. To demonstrate this mode of operation, 1.5 ..s long beam pulses are accelerated in six fully loaded structures in the CLIC Test Facility (CTF3) Linac. The final beam energy is compared to the input RF power of the structures, proving the efficient energy transfer

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