A 20 kA Test Bench for High-Precision Current Measurements

The d.c. currents in the LHC dipole and quadrupole chains will require settings and adjustments with a precision of a few ppm. For an ultimate current level of 13 kA this represents an unprecedented accuracy. Compared to the requirements of previous accelerators at CERN, such as the LEP, this is a factor of ten better in accuracy at more than twice the current. State-of-the-art, zero-flux current transducers from Industry will be used for the precision measurements. As no existing laboratory would be capable of performing the calibrations of these transducers to the required precision, a major upgrading of the current Standards laboratory at CERN was decided. The paper describes the various phases of the project, from field calculations and design to construction and final commissioning of this unique test bench. The highly automated facility allows determination of off-sets, linearity and drift of transducers up to 20 kA but provides equally the means to study the sensitivity of the transducers to external stray fields as generated by currents in adjacent busbars

Noise Reduction on the LEP bunch current measurement system

The lifetimes of coasting beams in LEP are computed from the difference of the bunch currents measured during a time interval of a few seconds. The quality of these measurements is presently limited by the noise figure of the bunch to bunch aquisition system. This paper describes comparative studies on the aquisition system in order to improve the noise figure by one order of magnitude. For this purpose three different principles, i.e. integrating measurements, peak hold circuits with internal timing (autotrigger) or peak hold circuits with external timing were studied. This paper describes the results of these studies

High-current performance evaluation of DCCTs

The evaluation of high performance DCCT's to the ppm level has never been an easy task. With the LHC demanding currents up to 13 kA, a whole series of problems has arisen in the accurate measurement of these devices. In order to tackle these problems, new facilities have been designed for laboratory measurements under full power operating conditions. These include a high performance low voltage 20 kA power converter, quasi-coaxial bus-bar structures, Kusters Bridge range extenders and a novel bipolar 0 - 10 A current calibrator with resolution and linearity better than ± 0.5 ppm. This paper will present an overview of the complete facility and give more detail on the new current calibrator. Initial results will be presented, along with application areas which advance the state of the art in this field of measurements

The CERN current calibrator: A new type of instrument

The LHC accelerator project will require an accuracy of similar to 10**-**6 in the control of current to the superconducting magnets. A new infrastructure for high current calibration is being created, based on DC current reference standards. This paper describes the design of a device generating an output current from 0 to plus or minus 10A with the required accuracy. 3 Refs

A novel current calibration system up to 20 kA

The Large Hadron Collider (LHC) particle accelerator project will require an accuracy of a few parts in 10/sup 6/ in the control of the current to the superconducting magnets. A new infrastructure for calibration is being built at CERN based on DC current reference standards rather than voltage. The paper describes the rationale, the infrastructure, the transfer methods, and the performance. (4 refs)