Operator's Manual
Issue 14 / Mar 2016
MercuryiPS
©2016 Oxford Instruments NanoScience. All rights reserved.
Page 57
5.2 Fast Rates / Slow Rates
The Fast/Slow button on the “Set Point / Set Rate” page (Figure 14) defines whether fast
magnet rate limits, or slow magnet rate limits will be applied. In general fast rate limits should
be used. The slow rates are usually only used for training magnets or after a major quench.
5.3 Editing the Rate Limits table
To add a row to the rate limit table, tap the “+” button in the bottom right corner (Figure 16).
This will add a row of the same rate limit type as the previous row with the “From” value set to
0.1mA greater than the “To” value of the previous row. To edit any of the values tap on the
value to open either a drop-down list to set the type or the numeric keypad to enter a value.
It is necessary that a limit type is specified over the complete current range (to 0.1mA
resolution) but it is not necessary that the rows of the same limit type are consecutive in the
table.
To remove a row from the table, tap the row number on the left-hand side, then tap the “-“
button in the bottom-left corner. A dialogue box will show a message indicating which row you
are about to remove. Tap OK to remove it.
5.4 Quench
See section 4.1 for a description of a quench event. The effect at the magnet terminals will be a
fast voltage transient which will appear at the power supply group terminals. When the voltage
exceeds the voltage limit defined for the group (e.g. GRPZ) in the configuration table
(section 4.4.3), the Mercury starts an internal timer. The timer keeps running while the terminal
voltage is above the threshold. During this time the rundown resistors of each magnet device
will switch in to dissipate some of the energy from the magnet to try to get the terminal voltage
below the limit (in case the quench is a false quench). However, when the timer exceeds the
transient time defined in the configuration table (section 4.4.6) the power supply stops trying to
dissipate the energy and drops into Quench mode. The “Quench” indicator on the Home screen
will be asserted in red. Typically one power supply device will enter Quench mode before the
others in the same group. At this point its Quench status is broadcast to all the other units in
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