1. ISIS Electrical Engineering Group
Mike Glover

2. ISIS Electrical Engineering Group Structure

3. ISIS Electrical Engineering Group Structure

4. Areas of Responsibility
ISIS Synchrotron Power Supplies
ISIS Extracted Proton Beam Line Power Supplies
ISIS Neutron Beam Line Chopper Power Supplies
Electrical Engineering of ISIS Control Systems for:
Vacuum Systems
Water Plant Systems
Electrical Engineering of Neutron Instrument Beam Line Installations

5. ISIS Synchrotron Power Supplies
Main Magnet “White Circuit”
14.4kV 650ADC 400AAC
Injection & Extraction Septum
5kA & 10kA 50V DC
Injection Dipole
50Hz 13kA 500µS Flat Top 100µS Rise Time
Ring Steering & Trim Quadrupoles
4 Quadrant 150kA/S 250 Amp Programmable
Fast Extraction Kicker Magnets
50Hz 40kV 5kA 500nS Flat Top 80nS Rise Time

6. Injection Septum
Deflects the injected beam into the aperture of the injection dipole magnet and onto the foil
200kW
5000 Amps
40V
1416 Transistor Regulator
100ppm stability

7. Extraction Septum Magnet Bend 21º 10,000 Amps 50V
11kV Supply Rectifier Transistor Regulator
4 Sets of 24 Transistor Banks
2304 Transistors

8. Extraction of Beam At Extraction Protons Circulating at 800 MeV
Two bunches with 200 ns gap
Extraction System
3 fast kicker magnets
deflect the beam into …
a septum magnet
which lifts it into the EPB
Kickers need to be fast to avoid beam loss
Go from zero to full field between passage of bunches

9. Extraction Details Kickers 3 units give 15 mr kick Rise Time 80 nS
Flat Top 500 nS
5000A
40kV
50Hz pulsed
Septum
~ 8 m downstream
8 Turn, 8900 A DC
1.8 m long (21 degrees)
Lifts beam out of machine

10. ESSO Ring Vacuum PLC Control System

11. ESSO Neutron Beam Line Installations
Complete electrical design
Electrical Supply
Detector Cabling
Chopper Cabling
Vacuum System Controls
Several kilometres of cabling per beam line

12. Power Systems and the ISIS Synchrotron
Andrew Kimber

13. Outline Main magnet systems MM Power Supply and the White Circuit
Capacitor bank replacement
UPS
Replacement 1MJ Storage Choke
Summary

14. Magnet systems Main Magnets 10 Bending Dipoles 10 Singlet Quadrupoles
10 Focussing Doublet
Quadrupoles.
Corresponds to 10 superperiods

15. Main magnet power supply

16. Main magnet power supply
For successful acceleration the same magnetic field is required in all the main magnets
Main Magnets per super period:
1 Dipole
1 Singlet Quadrupole
1 Doublet Quadrupole
How do we connect these?
One power supply per super period
Main Magnet System operates at 14.4kV
Current changes from 250A to 1050 Amps
Peak Power = 15.1 MVA
For 10 super periods the Peak Power
Required = 151 MVA
Excessive Power Required !

17. Main magnet power supply
Magnets have Inductance
Inductance can store energy E = ½ LI2
Capacitors also store energy E = ½ CV2
Resonate the stored energy between Inductor and capacitor:
With no losses in the system the impedances of the Inductance and the Capacitance would be identical and energy would be transferred with an alternating current between them and at a resonant frequency.
Inductance reactance XL = Capacitive reactance XC
ωL = 1/ωC ω = 2π f
Resonant Frequency f = 1/(2π√LC )

18. Main magnet power supply
Normal Temperature Magnets have Resistance
Capacitors have losses
Cables have losses
If the losses << Inductance we have a high ‘Q’ oscillating system.
We just require to supply make up power for the resistive and AC losses in the Magnets, Cables and Connectors.

19. The White Circuit
WHITE CIRCUIT M G White, Princeton (1956) CERN Symposium
Oscillate the magnet cell using capacitors and choke.
Connect all the magnets together electrically and same current flows through each magnet.
Permit DC bias current through split choke secondary winding
Power required is to make up for the resistive losses in the copper, ac losses in the magnets and power supply losses.
IM = IDC – IAC cos ω t
Total of 1.75MW (150MVA peak for non resonant circuit)

20. The White Circuit

22. Main magnet power supply
Replace capacitor bank with smaller more efficient units.
Replace the Motor Alternator Set with a UPS System
Replace the Choke.
Split the Choke into 10 separate units and build spare as well.
PROGRESS TO DATE
Capacitor bank replaced (2002)
UPS system currently on order.
Build a scale model to prove theory of split choke.
Scale model chokes currently being ordered.

23. Old Capacitor Banks

24. New Capacitor Banks Replaced in 2002 Smaller units, space used for
1 old bank is now used for 5.

25. Motor Alternator Set

26. Previous Motor Alternator Set
Brentford
Excitation
PSU 12KVA
Mains supply
5KV
single
phase
3.6KV
single
phase
Storage
choke
and main
magnets DC
Motor
Alternator
shaft
transformer
Phase locked to
ISIS 50Hz reference
signal
Electromechanical
Single phase output
2 phases connected line to line and 1 disconnected
Alternator phase locked to ISIS 50Hz reference
100Hz induced harmonic between raw mains and reference signal

27. Current Motor Alternator Set
Brentford
Excitation
PSU 12KVA
Mains supply
Phase locked to
ISIS 50Hz reference
signal
UPS
5KV
single
phase
3.6KV
single
phase
Storage
choke
and main
magnets DC
Motor
Alternator
shaft
transformer
Phase locked to
ISIS 50Hz reference
signal
Alternator and UPS phase locked to ISIS 50Hz reference
Factor of 2 improvement in AC stability

28. New UPS system Motor alternator set replaced with 4 300KVA units
three
phase
720V
single
phase
3.6KV
single
phase
Storage
choke
and main
magnets
transformer
Gray converter
circuit
Motor alternator set replaced with 4 300KVA units
(1 redundancy)
UPS units currently on order
Installed by Q4 2004

30. Storage Choke Current 1MJ, 2H Storage Choke
Ex-NINA, manufactured in the 1960’s
Ten interleaved primary and secondary windings
Choke windings and core: 90 tonnes
Total weight (inc. oil): 120 tonnes
30 years of service
State of insulation unknown, leaks oil, failure would result in ISIS being down for extended period of time

31. Replacement chokes Current 2H storage choke
10 off replacement 200mH chokes
…X10
1/5 scale models 40mH
Minimise financial and
technological risk
Due September 04
Full scale prototype/spare

32. Replacement chokes
Most probable design is a ‘frame’ type storage choke
Energy stored (air gaps) = ½ L I2
Energy stored/unit volume = ½ μ0 B2
Calculate dimension of air gaps
For 200mH, 1010A, 100KJ, 0.9T: Volume ~0.3m3
Size and distribution of these critical in controlling losses

33. Replacement chokes
Testing of scale models to take place September 2004
Losses
Stray magnetic fields
Leakage inductance
Linearity
Noise (mechanical)
Cost

34. Summary New capacitor banks Installed 2002 New UPS system
Installed by Q4 2004
New split choke system
Scale model testing Q4 2004
Prototype and production chokes 2005/6