High-performance Beam Research Articles

The AGLAE scanning nuclear microprobe setup

This paper gives a description of the recently installed scanning nuclear microprobe at the Accélérateur Grand Louvre d'Analyse Elémentaire (AGLAE) ion beam laboratory. The setup is based on the commercially available system from Oxford Microbeam, including a triplet focusing system, target chamber, slits and scanning coils. Some modifications have been made to simplify the procedure for extracting and forming the beam probe. Also, a high performance beam scanning and data acquisition system has been adopted.

Nutating subreflector for a millimeter wave telescope

Nutating a Cassegrain telescope’s secondary mirror is a convenient method of steering the telescope beam through a small angle. Using this principle we have constructed a high performance beam switch for a millimeter wave telescope. A low mass, graphite-epoxy laminate secondary mirror is driven by linear electric motors operated in a frequency compensated control loop. By design, the nutator exerts little net oscillating torque on the telescope structure, resulting in virtually vibration free operation. The inherent versatility of beam switching by subreflector nutation allowed us to test a variety of switching waveforms without making any hardware changes. To reduce the peak stresses on the mechanical linkage between the mirror and the motors and to attain a minimum transition time between mirror positions, we use a digitally generated driving waveform tailored to the system’s transfer function. The nutator can shift the telescope beam by 10 arcminutes, a 1.25° rotation of the 75-cm-diam secondary mirror, in an interval of 8 ms and it can sustain a switching frequency of 10 Hz.

Formation of p-n junctions and silicides in silicon using a high performance laser beam homogenization system

The paper presents a Nd-glass laser system comprising a high-performance beam shaping and homogenizing system which provides a rectangular laser beam having residual intensity fluctuations of less than 1% and 2% on the macroscopic and the microscopic scale, respectively. Two examples illustrate the high quality of the beam: First, p-n junctions of 0.3 depth were formed exhibiting an excellent electrical quality which was proved by EBIC measurements. Second, on the basis of the high degree of homogeneity the energy dependence of silicide formation could be precisely determined. By RBS and TEM investigations the conditions of heteroepitaxial growth of NiSi2 were studied.

The high-performance beam deflection system of EL3

A new concept of beam deflection was developed and implemented to achieve the high throughput and resolution performance of EL3. It combines the advantages of raster and vector writing techniques by dividing the field into overlapping subfields which are addressed by stepped raster magnetic deflection. Within each subfield electric deflection vectorially writes the pattern elements at high speed. The advantages of dual channel deflection and yokes within the projection lens are fully exploited. The repetitive raster deflection pattern permits the use of an automatic calibration system which corrects beam positioning errors of both deflection channels for fields up to 10 mm. Automatic calibration is utilized to assure good pattern overlay between optical and e-beam lithography tools to eliminate dedicated tool restrictions. It establishes subfield matching so that patterns are stitched together properly. In addition, overall field size and linearity are controlled to the accuracy and stability required. This paper discusses key aspects of the entire deflection system design, its components, and highlights compatibility questions and trade-offs between them. Specific problems such as thermal stability, speed/accuracy trade-offs, noise sources, and their solutions are presented. Calibration data are presented to illustrate the accuracy and stability achieved.