ISAC commissioning, tuning, energy adjustment, beam delivery to experiments

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ISAC commissioning, tuning, energy adjustment,
beam delivery to experiments

• R.E. Laxdal
• TRIUMF

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ISAC I ISOL POST-ACCELERATORS
High-Energy Experiments ISAC I (2001)
Thick/Hot Target
Beam Dump
DTL1
high-energy proton beam
S0
Heated Tube
Production Accelerator TRIUMF 500
MeV Cyclotron DRIVER
Ion Source
RFQ
A/q?30
ISAC I Low-Energy Experiments (1998)
Ion Beam
Isotope Separator
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ISAC-I Accelerator

• OLIS
• Stable beams
• LEBT
• All-electrostatic (2keV/u)
• 11.8MHz multi-harmonic pre-buncher
• 35 MHz RF Quadrupole
• E2?153keV/u
• A/qlt30
• MEBT
• Stripping foil
• 35MHz rebuncher
• 105MHz Variable Energy DTL
• E0.15-1.53MeV/u
• A/Qlt6
• HEBT
• Diagnostic section
• 11.8/35MHz rebunchers

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ISAC 35MHz RFQ

• 4 rod, Split ring structure
• 74kV/85kW cw, Q8400, R/Q4.4
• No bunching section
• ?s-25deg, 80 capture
• Reduces longitudinal emittance

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Medium Energy Beam Transport

• Section 1
• Matches Beam to Stripping Foil
• 105MHz 3-Gap Split Ring Bunch Rotator
• 5.9/11.8 MHz Chopper
• Section 2
• Charge Selection
• Section 3
• Matching Section to DTL
• 35 MHz Two-gap Spiral Rebuncher

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ISAC Separated Function DTL

• Acceleration by five IH tanks
• Quadrupole triplets for periodic transverse
  focussing
• Three gap split-ring bunchers for periodic
  longitudinal focussing

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High Energy Beam Transport

• Delivers accelerated beam to two major beamlines
• Two bunchers
• 11.8MHz (?1.8)
• 35.4MHz (?3.2)
• Diagnostic station for accelerator tuning

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ISAC-I Commissioning

• Staged commissioning
• Test 1 partial RFQ (7 ring)
• Test 2 full RFQ (19 ring)
• Test 3 MEBT and DTL tank 1
• Test 4 full DTL
• Test 5 HEBT and bunchers
• Diagnostic station moved after each test
• Analyzing magnet plus emittance rig
• First beam to experiment April 2001

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Test 1 LEBT and 7-ring RFQ

• measured RFQ acceptance and transmission

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• Collimators provides well defined centered beam
• Steering plate allows calibrated off-centering

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Test 2 Full RFQ

• Beam quality/capture as expected
• ?z0.5?keV/u-ns
• Matches to beam simulations

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Test 3 MEBT and DTL Tank1

• Studied energy variability
• Measured beam quality
• ?z0.5?keV/u-ns
• Studied effect of stripping foil

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Test 3 Chopper

• Dual frequency chopper (5.9/11.8MHz)
• Deflects away unwanted micro bunches

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Test 3 Transverse Emittance

• Measured emittance after
• Stripping
• Acceleration in Tank 1

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Test 3 Foil Studies

• Studied multiple scattering in foil and foil
  aging

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Test 4 - DTL

• Variable energy works as designed
• IH tanks provide discrete energy jumps
• Detune V and ? in last operating tank
• Transmissiongt95
• Beam quality good over full energy range

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DTL - New Development

• Extended energy range for accelerated beams
• Low range extended from 153keV/u to 120keV/u
• High range extended from 1.53MeV/u to 1.8MeV/u

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• Stable Accelerated Beam
• 4He1, 12,13C3, 14,15N4, 16O4, 20,21Ne4,5 and
  24Mg6 have been delivered to DRAGON and TUDA
  since April 1, 2001
• Beam Tuning
• Physicist establishes tune
• Beam delivered 24hrs/day
• Operations - foil replacements, energy changes,
  hardware resets
• Radioactive Accelerated Beam
• First Accelerated RIB beam July 25, 2001
• 2x107 pps 8Li2
• 20,21Na5 has been delivered to DRAGON, TUDA in
  Oct. 2001 (6x108 pps)
• Beam Tuning
• 16O4, 20,21Ne5 used as pilot beam
• switch from pilot beam to RIB is straightforward

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30Na 74Rb Yield vs Driver Current
30Na
Yield Ratemeter
50 mA Protons
74Rb
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SCHEMATIC of TIME DEPENDENCE for DRIVER CURRENT
with HIGH POWER, ISOL TARGET TEMP. RELEASED
YIELD

• Optimum Driver Current Pulse Lengths
• gtgt Half-life, Diffusion Effusion Times
• gtgt Thermal Time Constants
• Typically several minutes
• Driver Current Stability
• Operating Temperature is Determined by Driver
• Yield, Effusion, Diffusion Determined by the
  Driver Current
• With Significant Beam Heating
• DRIB/RIB gt DI/I

t1/2 ,tE, tD ?? Thermal Time Constant
t1/2 ,tE, tD gt Thermal Constant
Tmax