Transcript Target Overview

MICE Target
Review
Chris Booth
Sheffield
12th June 2006
Overview
• Mechanical Support
– Heavy frame, precisely located on floor
– gives location w.r.t. beam pipe
– Carries support for target mechanism
• EM Drive Unit
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Stator body containing series of coils
Ceramic liner (vacuum seal)
Ceramic bearings
Optical readout windows (complete vacuum system)
Shuttle: magnets, shaft, target, readout vane, ...
• Isolation System
– Jacking mechanism
– Bellows (200 mm travel)
– Gate valve
• Electronics to Drive Target
– Optical position readout
– Electronic control & commutator system
– Hex bridge high current drive(s)
Chris Booth
University of Sheffield
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Drive Details
• Stator
– 24 coils in triplets, driven
3-phase
– Water cooling system –
copper pipes
– Epoxy potting (thermal
path)
– Thermocouples between
coils
– Steel end plates
– Aluminium cylinder case
– Ceramic vacuum liner
Chris Booth
University of Sheffield
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• Shuttle
– 3 radial magnets (“surf” EM travelling wave provided by
coils)
– Cross-shaped (or square?) titanium shaft (in crossshaped (square) bearing aperture) maintains alignment
– 11030 mm3 Ti target (radiates beam heating)
Chris Booth
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University of Sheffield
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• Shuttle (continued)
– Stop (to prevent shuttle dropping)
– Optical readout vane (interrupts 3 laser beams)
Chris Booth
University of Sheffield
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Isolation System
• Jacking mechanism
– Raises target’s lowest position
well above beam
– Stepping motor + position
transducer
– Hand crank if motor failed
– Limit switches, for interlock
• Bellows to allow movement,
maintaining vacuum
• Gate valve
– closes to isolate target volume
from ISIS vacuum
Chris Booth
University of Sheffield
6
Position Readout
• 3 remote lasers in control area → optical fibres
– Fibre → optical alignment system around windows &
position sensing vane
– Collimator & lens give focused spot at vane
– Vane: comb of 0.3 mm wide teeth (pitch 0.6 mm)
– Transmitted beam → lens →collimator → return fibre
→ optical sensor (control area)
• 2 beams in quadrature
–  direction of movement
– resolution = pitch÷4 = 0.15 mm
• 3rd beam interrupted by single tooth (other side
of vane
–  absolute position
Chris Booth
University of Sheffield
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Control & Drive System (details in PJS CM talk)
• 4 modes
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Park → Hold
Actuate enable
Actuate
Hold → Park
• Park → Hold & Hold → Park
– Do not rely on position sensing
– Slow
– Low current (~3 A)
• Actuate enable
– Interlocked with ISIS
Chris Booth
University of Sheffield
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Control & Drive System (2)
• Actuate – triggered by ISIS Machine Start
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High current (? 80 A) – accelerates target down
Phase controlled by position sensing
½ way down, current (force) reversed
Decelerates to maximum depth; accelerates up
½ way up, current reversed again
Decelerates to Hold position
Switches to Hold mode
• Power electronics
– Trickle charged capacitor bank power supply
– Hex bridge (bidirectional switches)
– High-current enhancements being developed by
Daresbury Power Electronics group
Chris Booth
University of Sheffield
9
Interlocks
• Gate Valve & Jacking Motor
– Target must not damage gate valve diaphragm
– Can only operate valve when jack is at upper limit
– Can only lower jack when valve is open
• Target Drive
– Only enter “actuate enable” when ISIS enable present
– Only actuate when stator temperature normal
– Allow “actuate enable” without “ISIS enable” only at
jack upper limit (Debug or test mode)
Chris Booth
University of Sheffield
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Operational Procedure
• Target drive installation with gate valve closed,
jacking mechanism raised.
• Pump down
• Open gate valve
• Energise coils to raise target to Hold
• Lower jack to bottom (operational) position
• Enable drive for triggers
When MICE is not operational:
• Use jack to raise drive mechanism
• Park & power off target drive
• Close gate valve
Chris Booth
University of Sheffield
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Fault Conditions
Over-temperature
• inhibit insertion.
Failure of target control or drive
• Target falls into beam.
• Major beam loss each cycle. ISIS trips after 3
pulses.
• Jacking mechanism used to raise target clear of
beam.
Vacuum leak in target drive
• Jack raises target. Gate valve closed.
Chris Booth
University of Sheffield
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Current Status
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Maximum drive current
Stroke
Repetition Rate
Peak Acceleration
10 A
39 mm in 60 ms
~3 Hz
15-20 g
Requirements
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Maximum drive current
Stroke
Repetition Rate
Peak Acceleration
Chris Booth
University of Sheffield
80 A (?)
24 mm in 20 ms
≥1 Hz
~100 g
13
Open Questions
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Details of titanium shaft – Oxford workshop
Type of ceramic metal seal – Indium/bonded
Details of optical windows – RAL/Sheffield design
Adequacy of stator cooling – modified cooling to be
tested (effect of eddy currents?); no. of coil banks
• Radiation damage to magnets
• Radiation damage to magnet glue?
• Radiation damage to optical components (fibre,
collimator, lens)
– Replaceable drive units, designed for rapid exchange
– Margin for increased laser power, increased current?
• Beam or electrical noise in thermocouples/cables
– Alternative devices?
Chris Booth
University of Sheffield
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