f Antiproton Production in Run IIa

1
Where weve been, Where we are, Where were
going
Run Ib Now Run IIa (Goal) Protons on Target
(p/cycle) 3.2 1012 3.8 1012 5.0 1012
Cycle Time (sec) 2.4 3.2 1.5 Production
Efficiency (p/106 p ) 15 10 20 Stacking Rate
(1010p/hour) 7 4 18
As read out on MTOR109
2
Why is the present stacking rate lower than Run
Ib?

• Cycle time limited stacktail cooling / core
  cooling issues
• When these are fixed, there is a factor of at
  least
• 3.2sec/2.4sec 1.3 to be gained in the stacking
  rate
• The hope is that the cycle time can be as low as
  1.5 sec
• The Production Efficiency is down due to
• AP1 - Target Station - AP2 alignment issues
• AP2 Aperture
• AP2 - Debuncher match (or lack thereof)
• Debuncher Aperture
• Combined effectp yield into Debuncher (10/15)
  Run Ib
• 67 Run Ib
• Or, Stacking rate is a factor 1.5 lower due to
  these problems

3
Improvements / Fixes installed during November -
December 2000 Shutdown

• Stochastic Cooling improvements
• Debuncher Cooling Bands 3 4
• 3.2 GHz mwave mode fix
• Stacktail noise floor fix
• Beamline improvements
• Roll corrected on AP1 line Dipoles
• Installation of new Debuncher Injection Septum
• Target Station improvement
• Lithium Lens motion control restored

4
Expected stacking improvement from Debuncher
Cooling improvements

• Bandwidth increased by 2
• Gain increased by 2
• (Depends on improvements that will be installed
  in early 2001)
• Two-fold impact on stacking rate
• ) Cooling rate in Debuncher increased by 4
• Note This does not translate into a stack rate
  improvement
• until the cycle time is lowered
• ) Dp/p ofps injected into Accumulator is 4
  smaller
• Þ Smaller ARF1 Bucket Area Required
• Þ Lower Stacktail gain required

5
Accumulator Stack Profile During Stacking

• Beam arrives on injection orbit from Debuncher
• Beam is moved with ARF1 to central orbit
• Stacktail cooling must sweep the new beam off
  the central before the next pulse arrives
• The Dp that must be cleared is twice the ARF1
  bucket hight

6
Accumulator Cooling Issues - 2.6 GHz Stacktail
Instability

• The stacktail cooling drives the beam at 2.6 GHz
• This causes the core to oscillate coherently at
  2.6 GHz
• This coherent oscillation is detected on the core
  momentum cooling and the stacktail pickups

• At high enough gain there is positive feedback
  via the path
• ST kicker core ST pickup
• Presently this begins to happen at stack sizes of
  40mA
• This limits the stacktail gain
• This will likely force us to use the 4-8 GHz
  momentum system for core momentum cooling.

7
Accumulator Cooling Issues - 3.2 GHz Microwave
Mode

• This mode prevents use of the stacktail D-kickers
• The consequence of this is uncorrected heating of
  the core by the stacktail system
• As the stack grows the heating gets worse
  requiring lengthening of the cycle time to allow
  the core cooling more time to work

8
Core 2-4 Schottky Signals

• No injected beam
• Stacktail ON!

Paul Derwent Slide 7
9
Coherent Beam Feedback

• Use Stacktail FB spectrum
• Convolute 1/Df and Gaussian Core
• Reasonable explanation of shape

Paul Derwent Slide 8
10
Accumulator Cooling Issues - Can the Stacktail
momentum cooling stack at 20 mA/hr?

• The maximump flux through the stacktail is given
  by the slope of the momentum distribution
• Paul Derwents measurements show a maximump flux
  of 301010p /hour for stacks of up to 70
  1010p

11
Stochastic Stacking

• Simon van Der Meer solution
• Constant Flux
• Solution
• Exponential Density Distribution generated by
  Exponential Gain Distribution
• Max Flux (W2hEd)/(f0p ln(2))

Using log scales on vertical axis
Paul Derwent Slide 2
12
Stacktail Performance

• Fit to exponential in region of stacktail
  (845-875 in these units)
• Calculate Maximum Flux for fitted gain shape
• Different beam currents

• Independent of Stack Size
• Max Flux 10x stack rate

Paul Derwent Slide 3
13
Cooling Issues - Conclusions

• Debuncher cooling improvements decrease cooling
  time by a factor of 4
• ? the Debuncher is ready for a 1.5 sec cycle time
• It is not clear the Accumulator is ready for a
  1.5 sec cycle time. Things to worry about
• Will the 4-8 GHz core momentum cooling be
  adequate?
• Have we fixed 3.2 GHz mwave mode?
• Is the core transverse cooling adequate for large
  stacks
• 3.2/1.5 2.1 Stacking Rate improvement only if
  the Accumulator can handle it.
• This gives a Stacking Rate of 8.5 mA/hr

14
Core 4-8 GHz Transverse Cooling
15
AP1 Debuncher Issues

• Restoring AP1 - Debuncher to their Run Ib
  performance would yield an additional 50
  increase in Stacking Rate
• Assuming the cooling fixes work, this increase
  would give a Stacking Rate of 12.8 mA/hr - this
  is probably a good lower bound of what will be
  achieved in 2001.
• Why is yield into Debuncher less than Run Ib?
• Changes to upstream end of AP1 - transport from
  AP1 to Debuncher not yet re-optimized
• Loss of Debuncher aperture due to cooling upgrade
• 2421 p mm-mrad now versus 2727 p from run Ia
• Replacement of trim dipoles with motorized quads
• Cant center cooling tanks
• This figure can be increased by a factor of
  5.0/3.8 when 5.0?1012 POT is achieved

16
Efforts under way to recover and improve on Run
Ib performance

• Target Station - AP2 alignment, optimize pulsed
  magnet setting
• Add trim dipoles to AP2 line
• Match AP2 line to Debuncher lattice
• 300 blowup of vertical emittance
• Debuncher Aperture improvements
• Motorize more quad stands (10 by summer 2001)

17
Jim Morgan 12/12/2000
18
One more thing to worry about
Stacking should not quench the Tevatron We
suggest implementing a MI abort that would be
pulled when

• RPOS in the MI is out of spec
• P1 or P2 line power supplies at incorrect setting
  or not properly regulating