The Slope Box

Figure 1. Slope Box Diagram

The slope box (or sloped box) is the interface between the control & monitoring system and the detector. The slope box takes DC power from the SBX power board and generates the bias voltage for the Ge detector (typically around 3500V) as well as the lesser bias voltage for the BGO detectors (~750V - 800V). The HV supplies of the slope box are programmable through EPICS. A demand HV value is written to a DAC in the slope box and the HV is a multiple of the DAC voltage. The slope box also has a multiplexed ADC that measures detector temperature, actual HV being applied and values of the various power supplies. Figure 1 shows the various connectors on the slope box and their purposes. The preamp connector is a signal output to the preamp, although the preamp connector can be different based on the Ge's segmentation (this one is for a segmented Ge). The BGO ring connector is a signal output for the BGO detectors surrounding the Ge, while the backplug is for the BGO behind the Ge. The High Voltage (HV) connector is for providing the bias voltage to the detector. Underneath the slope box is a metal belt, which is for securing the slope box and SBX against the detector.

In the previous implementation of Gammasphere before upgrades, the slope box was intimately associated with the VXI modules in the 'shack'. The VXI modules provided DC voltage and a serial interface to the slope box, and a processor board (an IOC, in EPICS parlance) converted changes in control process variables into serial messages to the slope box. These messages included commands to set the DAC or to read out the ADC. After updates, the Slope Box isn't significantly different; the main changes have been in what happens to signals after they come from the Slope Box, particularly in regards to the SBX.

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