RMS Focal Plane

RMS Focal Plane
The recoil mass spectrometer (RMS) focal plane may be located at varying distance from the last RMS focussing element according to the experiment's requirements. Most experiments will be satisfied with a focal plane distance of approximately 43 (converging mass mode) or 93 cm (diverging mass mode). In most cases the choice of mode does not matter and our preferred mode of operation is the converging mass mode. This allows for smaller image sizes and hence, smaller detectors and chambers.

Fig. 1 - A photograph of the final focal plane of the RMS. The setup is for converging mass mode and the ionization chamber is mounted behind the MCP.
A photograph of the RMS with the focal plane in the foreground is available. In converging mode, the focal plane chamber is bolted directly to the exit flange of the last RMS quadrupole. In diverging mode, a 20.3 cm to 30.5 cm diameter flange, a removable 30.5 cm diameter, 50 cm spacer, and a large chamber with dimensions 38.1 x 70.9 x 43.4 cm. (HxWxL). The chamber has a removable back flange so that other devices such as an ionization chamber may be added. All parts are mounted on platforms attached to rails which allow rapid changes or repairs to experimental equipment.

The PSAC or MCP is housed in the large chamber and is situated directly over two 300 l/s turbomolecular vacuum pumps. Four ports are available upstream for a slit system to collimate the focal plane should it become necessary. Two ports reserved for vacuum gauges are on either side of the PSAC housing.

Focal plane detectors

There is a variety of detector systems developed to be used at the focal plane of the

For detailed questions about the use of Focal Plane Detectors contact Krzysztof Rykaczewski.

Digital data acquistion system

The HRIBF supports the Digital Data Acquisition System for most experiments at the focal plane of the RMS. It is based on XIA's DGF4C (40 MHz, 12 bit) boards, which offer the flexibility of use with almost any kind of detector system. The available modes of operation include, MCA-singles, time stamped list mode, time stamped list mode with pulse shape storage (50 μs long). A brief overview of applications can be found in [1]. Currently, experiments using up to 100 independent channels are supported.

For detailed questions about the use of the Digital Data Acquisition System contact Robert Grzywacz.


  1. R. Grzywacz, Nucl. Instrum. Methods Phys. Res. B 204, 649 (2003).

For questions about this page please contact the HRIBF User Liaison.

This file last modified Friday March 28, 2008