13
DLD8080 R4.30 & R4.31 Manual
High voltage sparks may seriously damage the detector anode/meander or the MCPs.
Observe the chamber pressure carefully every time the high voltage is turned on. Switch
off the high voltage immediately in case of a temporary pressure rise by an order of
magnitude or more. This indicates high voltage sparking.
If sparking occurs, turn down the high voltage immediately and wait some time (up to 5
min.). Start the “Start-Up” procedure again with an increased ramp time. Turn off the high
voltage completely, stop the procedure and call your provider for further assistance, if is
it not possible to reach the operation voltage without sparking.
Figure 3: Schematic sketch on voltage ramping during “Start-Up” procedure.
The detector starting operation voltage for “MCP-B” is given in the specification sheet.
The voltage for “U_DLD” should be kept fixed at + 400V in relation to “MCP-B” .
The voltage for “MCP-B” is always given in reference to the MCP front voltage “MCP-F”.
(The Surface Concept HV Power Supply keeps the relation between “MCP-B” and “U_
DLD” fixed at +400V automatically and the “MCP-F” voltage corresponds directly to the
external reference voltage of the HVPS. See the manual of the SC HVPS for further details).
Note
Example:
Assume the following operation voltage for “MCP-B”: +1,900V in respect to “MCP-F”. A ramp time
of approx. 5 min. should be used to increase “MCP-B” to +1,900V (“MCP-F” + “MCP-B”). In parallel “U_DLD”
must be ramped to a voltage of +2,300V (“MCP-B” + 400V), always keeping a voltage difference between
“MCP-B” and “U_DLD” of + 400V. always keeping a voltage difference between “MCP-B” and “U_DLD” of +
400V and a voltage difference between “MCP-F” and “MCP-B as specified in the specification sheet.
The analogue readout electronics have been adjusted to optimized detector voltages.
The starting operation voltages are given in the specification sheet of the detector.
Please note that one cannot compensate a voltage lower than the specified operation
voltages by increasing the intensity to the detector. This will only lead to complete false
measurement results.
DLD8080 R4.30 & R4.31 Manual | Surface Concept GmbH
