Collaborators: Chuck Schmidt, Henryk Piekarz,

1
HINS Ion Source and LEBT
Douglas Moehs Muon Collaboration Video
Conference Fermi National Accelerator and
Rutherford Labs February 23, 2007

• Collaborators Chuck Schmidt, Henryk Piekarz,
• Tom Page and Sami Hahto (LORENTZ)

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HINS Ion Source Requirements

• LEBT beam parameters based on RFQ specifications
• Beam current accounts for losses in RFQ
• Pulse length includes 0.1 ms to account for
  chopping
• In addition we desire
• 95 front end availability
• Greater than 12 weeks maintenance cycle

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The Plan

• Refurbish and upgrade an existing LEBT
• Utilize the original H Dual-Plasmatron Ion
  Source
• Demonstrate 50 kV operation
• Move system to HINS hall
• Develop 1 duty factor magnetron
• Why Use a Magnetron
• Test Bench Performance
• Current
• Approximate Emittance and its time dependence
• Simulations
• Remaining challenges
• Merge ion source and LEBT
• If the magnetron is not ready initial HINS test
  can use an H beam

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LEBT Refurbishment

• Existing magnetic LEBT
• 2 Solenoids lens
• Gate valve
• Column good to 80 kV
• 50 kV tests
• Dualplasmatron (H)
• 15 mA, 66 us, 15 Hz
• Upgrades
• 1000 l/s vacuum pumps
• New solenoid PS on order
• Long pulse arc supply
• Safty system beam stop

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Why Use a Magnetron

• Magnetrons can easily produce desired currents
• Emittance scales roughly with aperture and
  current
• For 15 mA a very small aperture can be used (lt 2
  mm dia.)
• At 15 mA any source could produce the desired
  emittance
• Note for 47 mA this may not be the case! (see
  next slide)
• We gain a lot of time for RF source developments
  to take place at other labs like the SNS, DESY
  and CERN
• Magnetrons have demonstrated long pulses
• The BNL source operates at 700 us, 0.5 df
• Fermilab has existing expertise and source
  components

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Historical Magnetron Emittance
Emittance Trend No attempt to normalize or
separate out cathode, aperture or
LEBT/pre-accelerator types. The green line is a
linear fit to the data and the pink curve
represents a square root fit to the data. These
emittance values were gleaned from the following
reference Schmidt, PNNIB, p.123 (1977) Alessi,
PNNIB, AIP Conf. Proc. 158, 419 (1986) Stipp,
IEEE TNS, 30, 2743 (1983) Smith, RSI 53, 405
(1982) Alessi talk associated with, AIP Conf.
Proc. 642, 279 (2002) Criegee, Peters et al., RSI
62, 867 (1991) Schmidt, PNNIB, AIP Conf. Proc.
158, 425 (1986) Moehs, IEEE TPS, 33, 1786
(2005) Peters RSI 71, 1073 (2000) Welton, PNNIB,
AIP Conf. Proc. 639, 160 (2002)
Average of XX and YY
New Data
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Straight Ahead Magnetron Test Configuration
Bellows for tilting source
Einzel lens
Emittance
solenoid
toroid
Ceramic column
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Source Performance and Current _at_1 Hz
Arc Voltage
Arc Current
Gas HV Pulse
Arc Power
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YY Emittance - Time Evolution
20 mA H- current -50 kV Source -40 KV Extractor
Approximate!!! Normalized, RMS Emittance 0.16
mm mrad
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LORENTZ Simulations
Sami Hahto
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LORENTZ Simulations
Future 50 keV operation Source voltage -50
kV Extractor -30 kV Einzel lens -33 kV IH-
45 mA, Ie- 90 mA Icoil 3300 Ampturns NOTE!
It is expected that this emittance value is high.
The cause Errors in the extraction region,
limited particle traces, unknown electron current.
Sami Hahto
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Remaining Challenges

• DF limited by cathode temperature (see slide 13)
• Try using Aluminum Nitride ceramics
• AlN has a thermal conductivity 100-200 times
  grater than Macor and 6 times grater than AlO2
  (Two sets on order)
• LEBT - magnetron integration
• Permanent magnet configuration required
• Needed for highly reentrant design (see LEBT)
• Stable power supplies!
• The Extractor, Acceleration and Lens voltages
  droop by 2 kV
• Acceleration supply on order
• Einzel Lens replaced by solinoids
• New emittance probes needed!! (see slide 14)

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Preliminarily Thermal Modeling
Tom Page
Typical Operating Temperatures for 0.135 duty
factor, average power 7 W
Expected Temperatures for 1 duty factor, average
power 28 W
14
Problem with Emittance Data

• Slit-harp configuration
• Rely on secondary electron signal
• Electron can jump from one collector to the next
• Cannot effectively remove all electrons without
  distorting the beam
• Dont know how to treat negative signals
• Unknown amount of error???