The 2004 SWAMP mission is to replace all pick-up boxes (that handle the high voltage). The new pick-up boxes are equipped with filters that will remove the interference from the VLF.
| Planning |
| ADC fit |
| HV changes |
| Noise Investigations |
| Log book |
| Runs |
| The 2002 maintenance manual (basic things still the same) |
| The 2002 SWAMP upgrade |
| The 2001 SWAMP upgrade |
| SWAMP team |
| Summary of work |
| Per Olof Hulth |
| Klas Hultqvist |
| Thomas Burgess |
| Christin Burgess |
The aim was to replace all old pick-up boxes with new ones with a VLF filter. After some initial testing this was done. After the change, B4 still picks up some of the VLF signal, which manifests itself as a low frequency noise source. This gives an additional noise peak in the ADC spectra below 50mV. In order to reduce the noise and optimize the ADC peak positions, most channels in B4 got changed high voltage. The channels most sensitive to the VLF are 1,2,13,41,42,44,69,70 and hence these channels also got an increased threshold, from 100mV to 150mV.
After the change, the channels in strings 5-10 picked up more of the 8MHz noise from the 1458 crate situated below the SWAMP crate. In order to solve this, the bandwidth limit of the SWAMP cards was changed from 10MHz to 7.5MHz. Furthermore, we realized that the noise picked up from the 1458 can be strongly reduced by just moving the OM cables as far away from the HV crate as possible. Our investigations show no evidence of the noise being picked up through the HV cables.
We're shipping 33 old pick-up boxes back to Stockholm. We're leaving two fully functional new pick-up boxes as spares, along with one new but opened pick-up box from which cards can be taken. The two VLF filter test pick-ups that were installed last year are also left as spares. Finally one old B4 pick-up box is left for emergencies.