Run IIa Plan Update Outline (MI) - v1
S. Mishra 9/13/02
Comments by M. Church 9/16/02
Re-edited by S. Mishra 9/30/02
1) Investigation of longitudinal
emittance growth on $2B cycles and $29 cycles
Potential Impact: Coalescing is presently tuned to maximize coalescing efficiency without regard to the longitudinal emittance of the coalesced bunch. If the desired mode of operation is a 2.1 eV-sec coalesced bunch in the Tevatron, the MI h=588 recapture voltage should be set to produce this bucket area. Then the h=28, 2.5 MHz, rotation voltage should be lowered (by a factor of »588/1113) to reduce the DP/P spread of the rotated beam to match this new recapture voltage. The coalescing efficiency will initially be lower, but reducing the amplitude of the coupled-bunch oscillations and the longitudinal emittance blow-up of the individual bunches should get us back to 270E9 per coalesced bunch for Tevetron injection.
Status: Two distinct longitudinal problems have been observed on both the $29 and $2B cycles, coupled-bunch modes and emittance blow-up of a single bunch. For both cycles, two MIRF cavity modes have been seen to interact with the initial coupled-bunch structure coming out of the Booster. Since both of the excited MIRF cavity modes are already passively damped, there are no residual fields from previous turns left in the cavities. Therefore; this can be viewed as a single pass transient beam loading effect on the HOM’s of the RF cavities. With this interpretation, it becomes clear that the only solution to the coupled-bunch problem is a bunch-by-bunch active damper. The large dipole oscillations associated with the coupled-bunch motion creates a large “effective” longitudinal emittance of the bunches which is particularly detrimental to the coalescing process and bunch rotation for pbar production. This effect is now much larger than the emittance blow-up of the separate bunches.
Plan of Action: Using the Booster quad damper as a bunch spreader does not result in a lower single bunch emittance at 150 Gev. What it does accomplish is reducing coupled-bunch motion by lowering the peak bunch current and making the bunches much longer compared to the wavelength of the HOM’s being driven in the RF cavities. The obvious penalty for using a bunch spreader on the $2B cycle is that beam is coming into the MI with a single bunch emittance a factor of two larger than on the $29 cycle.
The plan of action should be first to reduce the coupled-bunch motion using an active bunch by bunch damper and then proceed to investigate the individual bunch emittance growth.
Initial damping tests will be done using either the old “green bomb” longitudinal damper or a modified version of the 7.5 MHz Finemet cavity.
Resources Required: A state of the art low-level front end for the bunch by bunch damper is presently being built by Bill Foster’s group of volunteers from PPD and CDF. A budget code with $500K should be established for the construction of the high power dampers.
Schedule: The complete damper system could be operational in 6 months requiring 67.2% of Wildman’s time.
Uncertainties: The exact power required for the high level damper is not known. By observing the excitation of the individual HOM’s we know that the maximum voltage generated in each cavity is £ 200V on a $29 cycle. Therefore a damper voltage of 200V X 18 cavities = 3600V could damp the fully developed oscillations. My proposal is to build a wideband RF system similar to the recycler with a peak voltage of 1500 volts. This should result in either the complete elimination or a substantial reduction of the coupled-bunch motion.
Priority: 1
2)
Commissioning of 53 MHz beam loading compensation for pbar coalescing
Potential impact: Will improve the coalescing efficiency for pbar at fixed energy. 8 to 10% improvement on the average coalescing efficiency is expected on high intensity transfers from Pbar.
Status: Need to optimize digital part of the
electronics. New up-convert mixer needs
to be implemented to reduce the 53 MHz noise level. Spare modules of down-convert, digital delay and up-convert need
to be made.
Plan of action: Study with beam
has been progressing well. It is not
fully commissioned.
Person in charge: Joe Dey
Resources required: John Reid will aid in the development of the new up
convert module. 10 % of his time is
required for a month. A HLRF technician
will make the spares. 10 % of their
time is required for two months. Ioanis
Kourbanis will aid in the commissioning of the beam loading compensation, which
is limited in progress to Pbar transfers. 25 % of his time is required for two
months.
Schedule: 12/30/02
commissioning should finish with new modules in place.
Needs: We estimate roughly $ 5,000 in parts.
Uncertainties: Not known at this time.
Priority: 1
3)
Further 53 MHz beam loading compensation commissioning
Potential impact: Will improve the longitudinal emittance up the ramp on all
high intensity cycles ($2B and $29).
Status: Need to implement time delay system to
track frequency sweep up the ramp.
Plan of action: Studies with beam will start after fixed energy part is done and commissioned. Parasitic studies with $29 and $2B will be needed.
Person in charge: Joe Dey.
Resources required: John Reid and Ioanis Kourbanis will be required. 15% of their time will be required for three
months.
Schedule: 3/30/03
Needs:
$ 50,000 is estimated to create a time delay tracking system for beam loading
compensation.
Uncertainties: Depending on the amount of beam loading reduction
achieved, a digital comb filter feedback system may be needed to gain further
reduction. A digital comb filter system
will require additional time and money.
Priority: 2
4) Improved Multiwires in the MI to TeV transfer
lines. This beamline is now assigned to V. Lebedev. He is defining scope of project.
Remove this from your list (Is long term operation of this line not MID responsibility anymore?)
Potential impact: Will improve our understanding of the transfer lines and
its match to downstream machines. It will be used to check day-to-day stability
of the transfer lines.
Status: We need to get 0.5 mm spacing wires wrt 1
mm spacing now. 1 mm spacing wire does not have resolution to see the small
motion of the beam. The present BPMs in the MI transfer lines do not work for
coalesced beam. We rely on the knowledge that the beam position is the same for
two beams. I disagree. BPM method is better.
Plan of action: We plan to give this job to PPD. They are already in the
loop of the Multiwire issues. Once the paddle are made we can exchange the
paddle in the tunnel.
Person in charge: Dave Johnson
Resources required: Priority wrt other
BD projects.
Schedule: 11/31/02
Needs:
About $5k for M&S.
Uncertainties: Not known at this time.
Priority: 3
5) Dampers in MI.
Status: It is being designed and in R&D phase.
Plan of action: Finish the design
and build the damper. We have already started purchasing part for an R&D
project on digital damper system. This will be a benchmark for all the other
dampers in the Main Injector complex.
Person in charge: G.W. Foster
Resources required: Some technicians,
50% time of Brajesh Choudhary, PPD physicists and beam time
Schedule: R&D Proof-of-principle
MAKING OPERATIONAL SYSTEM
Needs: Time and $100k
Uncertainties: Not known at this time.
Priority: 1
6) 53/2.5/7.5 MHz BPM's in the MI
Potential impact: We plan to accelerate antiproton beam in the Main Injector
using 2.5(7.5) MHz RF systems. This will eliminate the coalescing process and
reduce the longitudinal emittance by about a factor of 2. At present MI BPMs
operates only at 53 MHz and we run blind for all other operation. This will
become a serious issue when we start accelerating with 2.5 MHz RF.
Status:
A 2.5 MHz design is in R&D phase for the Recycler. Once the Recycler
project is done we will perform a similar upgrade for the Main Injector.
Plan of action: Finish the Recycler project. Develop a 2.5 MHz BLT system
for the Main Injector using the Recycler technology. This will enable us to
start transfer of beam from the Recycler to the Main Injector and accelerate
with 53 MHz systems to start.
Person in charge: Brajesh Choudhary
(after he is done with Recycler)
Resources required: Same as the
Recycler BPM development.
Schedule: 5/1/03
Needs: Same
as the Recycler BPM development. It will also require $600k.
Uncertainties: The current R&D fails to meet the design
specifications.
Priority: 1
7) 2.5 MHz acceleration of pbar in the
Main Injector
Potential impact: This will remove the coalescing process for pbar, hence
will improve pbar longitudinal emittance and efficiency of beam transfer from
MI to Tevatron.
Status: Conceptual design exists. No serious work
has happened due to manpower limitations. Needs 2.5 MHz BLT and RPOS feedback
loop in MI. Needs LLRF software.
Plan of action: Get LLRF group to work on this project once they are done
with Recycler. Get the digital BLT to work in MI at 2.5 MHz. Improve the 2.5
MHz feedback detectors S/N.
Person in charge: Chandra Bhat
Resources required: LLRF group. 50% of the Brian Chase and Keith Meisner time
will be required for 3 months. Digital down convert cards for the BLT is being
developed for the Recycler. This will be copied for the Main Injector. It needs
Warren Schappred full time effort.
Schedule: 3/30/03
Needs:
Beam time for development of this ramp, about 20 shifts. $100k for feedback
system and BLT will be required.
Uncertainties: Not known at this time.
Priority: 1
8) General diagnostics
Improvements
Potential impact: This will provide a stable data source for the MI
operation.
Status:
Main Injector has several operational instruments, for example DCCT, Toroid,
Flying wire, SBD, RTD720 attached to Resistive Wall Monitor. One of the major
short coming has been that these instruments are not cross calibrated, does not
have reliable or user friendly operation, no or little documentation and semi
stable data logging of the instrumentation.
Plan of action: Get physicists, software professional and engineering
staff responsible for these devices and document these short coming and why.
Develop a plan of action based on whose end needs work.
Person in charge: Dave Capista
Resources required: Will require about 0.5 FTE from MID, 0.5 FTE from RF&I
and 0.5 FTE from Controls.
Schedule: 3/31/03
Needs: No
new hardware is needed at this time. All development and calibration can be
done with parasitic beam.
Uncertainties:
Priority: 1
9) Tune meter for pbar operation
Potential impact: This will improve
day to day operation of the antiproton acceleration cycle.
Status: At present we do not measure tune of the
antiproton through the ramp. We rely on the setting of the Main Injector using
the proton beam. Although this is rather reliable for the MI magnet quality
small change in tune is required once in a while to keep the efficiency up.
Plan of action: Develop a tune meter based on pbar design using the Main
Injector Strip line detector. We will be required to split this signal between
BLT and tune meter.
Person in charge: Denton Morris
Resources required: VSA and a better
interface to it than GPIB. We need help from CD in developing a better
interface than GPIB for these devices.
Schedule: 3/31/03
Needs: $100k
Uncertainties: None
Priority: 1
10) Improvement in MI ramp and closure
programs (this sounds like two
different projects)Kind of but has one goal to
reduce injection oscillation differences between MI cycles.
Potential impact: This will reduce the transverse emittance growth for
protons.
Status:
At present the MI ramp and closure are cycle independent for example operation
closes the injection on $29 cycle and all other users of beam at that time on
other cycle suffers from small injection oscillation, hence emittance growth.
This has to do with reset of the MI bus ramp and also the extraction of beam
being different from Booster on different cycles.
Plan of action: Study and document reset dependence of the MI ramp. Study
and document the injection oscillation on different cycles. Improve the MI
reset ramp for cycle in the time allocated by present ramp. Improve MI closure
software to take into account of different cycle. This needs new calibration
table for each cycle.
Person in charge: Bruce Brown
Resources required: 50% of Guan Wu’s time for 1 month. Parasitic study cycle
to change MI reset.
Schedule: 11/30/02
Needs: No
new hardware is required.
Uncertainties: None
Priority: 1
11) Tune and chromaticity calculator
programs
Potential impact: Reliable operation
of MI
Status:
At present we measure the tune in the Main Injector one step at a time
manually. The chromaticity is derived from these data offline. This is not only
a time consuming process and at times undocumented process.
Plan of action: Develop software that can automate this manual process.
Person in charge: Guan Wu
Resources required: New pinger in the Main Injector that is capable of pinging
beam up to 150 GeV and has one turn pinging capability.
Schedule: 12/31/02
Needs: $100k
for new pinger
Uncertainties: None
Priority: 1