D+D minimum energy Ecm = 150 keV which corresponds to Ed=150 keV/u or Ed=300 keV. Therefore we need a threshold below this.

Test 1 - Current status

Current slow comparator threshold is 0x64 (1 MeV). ADC data items rate in all FEEs is essentially zero with this threshold. (except aida03 and aida04). Aida15 and 16 also show ~1k rates when DSSD4 current is fluctuating.

Pulser was set to find point it is cut off by the threshold. Attachments 1,2,3 show 1.8L for nn channels with the pulser set to 570,550 and 530. Over this range pulser disappears. Estimate 550 is equal to ~1 MeV.

Test 2 - Noise level at lower threshold 200 keV

Threshold set to 0x14 (200 keV). Pulser kept at 550 for the time being to gauge location of noise compared to pulser. Attachments 4,5 show 1.8L for nn and pn channels respectively. Some noise observable at low energy.

Note zero energy is around 32500 channels. In nn channels (attachment 4) pulser is to the right of the noise peak, wheras in pn channels (attachment 5) pulser is to the left of noise peak.

Attachment 6 shows data rates with pulser off. Rates okay, only aida15 has very high rate (80k), rest of channels <5k.

Test 3 - Noise level at lower threshold 100 keV

Threshold set to 0xa (100 keV). Pulser kept at 550 for the time being. Attachment 7 shows data rates with pulser off. Rates significantly higher all round. Half of channels >50k, some >100k.

Attachments 8,9 show 1.8L for pn and nn channels respectively. A lot more noise observable at low energy. Pulser peaks generally overshadowed by noise. 100 keV probably too low to set threshold.

Test 4 - Noise level at lower threshold 150 keV

Threshold set to 0xf (150 keV). Pulser kept at 550 for the time being. Attachment 10 shows data rates with pulser off. In general rates are pretty low. Most channels <1k. Aida15 and 16 pretty high.

Attachments 11,12 show 1.8L for nn and pn channels respectively. Noise observable at low energy but in general less than that of the pulser peaks.

Test 5 - D+D pulser peak at lower threshold 150 keV

Theshold kept at 0xf (150 keV). Pulser set to 180 (should be about 300 keV based on Test 1). This should be the level of d+d at our lowest beam energy.

Attachments 13,14 show 1.8L for pn and nn channels respectively.

Test 6 - D+D pulser peak at lower threshold 200 keV

Theshold increased to 0x14 (200 keV). Pulser kept at 180 (should be about 300 keV based on Test 1). This should be the level of d+d at our lowest beam energy.

Attachments 15,16 show 1.8L for nn and pn channels respectively.