Oxford Instruments NanoScience MercuryiPS - Temperature Safety Limit (Limit (K)); Level Safety Limit (Limit (L)); Intelligent Switch Function (Sw Intel)

Operator's Manual
Issue 14 / Mar 2016
/ UMC0071
MercuryiPS
©2016 Oxford Instruments NanoScience. All rights reserved.
Page 50
4.4.11 Limit (K)
This is the temperature threshold below which it is safe to run the magnet (see above). If the
magnet temperature signal is above this value the iPS group will not ramp up. If the magnet is
already energised the iPS group will enter auto-rundown mode. This will ramp the magnet to
0A at a safe slow rate. If the magnet is persistent, the iPS group will ramp up to the last known
magnet current, turn on the switch heater to ‘pick-up’ the magnet, ramp the magnet to zero,
then turn off the switch heater.
4.4.12 Limit (L)
This is the level threshold above which it is safe to run the magnet (see above). If the magnet
Helium level signal is below this value the iPS group will not ramp up. If the magnet is already
energised the iPS group will enter auto-rundown mode. This will ramp the magnet to 0A at a
safe slow rate. If the magnet is persistent, the iPS group will ramp up to the last known magnet
current, turn on the switch heater to ‘pick-up’ the magnet, ramp the magnet to zero, then turn off
the switch heater.
4.4.13 Sw Intel
This parameter switches ON/OFF the Intelligent Switch function.
 In the “Sw Intel” = OFF state the switch heater current is either 0mA, when the switch
heater is OFF, or a constant value determined by the “Sw Cur” parameter (see above),
when the switch heater is ON.
 In the “Sw Intel” = ON state, when the switch heater is also ON, the total power
dissipated in the switch is kept constant based on the equation:-
 
 
R
RI
V
RIP
Switch
leadsop
op
SwHtrSwHtrlSwitchTota
2
2
*
*


where R
SwHtr
is the resistance of the switch heater entered in the table (see below),
R
Switch
is the resistance of the superconducting element of the switch when it’s in its
“normal” state, a value entered in the table (see below), V
op
is the iPS group output
voltage, I
op
is the iPS group output current, R
leads
is the lead resistance a value entered
in the table (see below) and P
SwitchTotal
is the target total power dissipated in the switch.