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Dave McGinnis April 15, 2010

How to Run the Tevatron Collider with Oodles of Luminosity and Send Gobbs of Protons to NoVa at the Same Time. Dave McGinnis April 15, 2010. Introduction. After the results of the LHC Chamonix workshop were published, a few of us at Fermilab started wondering :

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Dave McGinnis April 15, 2010

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  1. How to Run the Tevatron Collider with Oodles of Luminosity and Send Gobbs of Protons to NoVa at the Same Time Dave McGinnis April 15, 2010 Run III - McGinnis

  2. Introduction • After the results of the LHC Chamonix workshop were published, a few of us at Fermilab started wondering : • does it makes sense to run the Tevatron longer than planned? • maybe until 2015? • We realize that the Recycler, which is a key component for the collider, is going to be cannibalized for Nova starting in 2011-2012 • We wonder is there any way to run the Tevatron and Nova at the same time? • That’s the whole point of this talk. Run III - McGinnis

  3. The Informal Organization • Physics case of Run III • State of the detectors • State of the accelerator • Luminosity in the Collider • Protons for Nova This talk Hmmm.. Run III - McGinnis

  4. State of the Tevatron Collider • The Tevatron Collider is operating at its peak performance. Currently: • The average yearly integrated luminosity exceeds 2fb-1. • The average weekly integrated luminosity exceeds 50pb-1. • The average peak luminosity is over 300mb-1/sec. • The Tevatron spends over 130 hours per week in colliding stores. Run III - McGinnis

  5. Tevatron Collider Performance Run III - McGinnis

  6. State of the Tevatron Collider • It is often stated that the Tevatron Collider complex is an ``aging machine,’’ • to imply that continued operations would be “a priori fragile”. • This is simply not the case. • Tevatron performance parameters continue to climb. • The store hours per week have risen dramatically over the years, from 70 hours per week in Run I to over 130 hours per week in Run II. • While every machine of this complexity needs constant maintenance • The overall outlook on maintenance and spares for the Tevatron, Main Injector, Recycler, and Antiproton source has remained unchanged for at least the past three years. Run III - McGinnis

  7. Role of the Recycler in the Tevatron Collider • Since the Tevatron is a proton-antiproton collider • it is limited by antiproton beam brightness. • The spectacular performance of the Tevatron Collider • is the culmination of many years of investment into the Main Injector, Recycler, and Run II upgrades • that substantially increased the antiproton beam brightness. • One of the major components of the Fermilab antiproton production capability is • the Recycler and its electron cooling system. Run III - McGinnis

  8. Role of the Recycler in the Tevatron Collider • The Recycler functions as a third stage storage ring for antiprotons • which reduces the load on the rapid stacking with stochastic cooling in the Antiproton Source. • Electron cooling in the Recycler, • which was considered by many as risky when it was first proposed. • condenses the antiproton beam to unparalleled beam brightness. • Without the Recycler and electron cooling, • experts estimate that the yearly integrated luminosity would be halved from its current level. Run III - McGinnis

  9. Planned Accelerator Upgrades for NoVa • At the end of the collider run: • Electron cooling will be decommissioned • The Recycler will be turned over to the neutrino program to act as a proton accumulator for the Main Injector. • The conversion of the Recycler to a proton accumulator is just one of a suite of upgrades to the accelerator complex for the neutrino program. Run III - McGinnis

  10. Planned Accelerator Upgrades for NoVa • 1. With the use of the Recycler as a proton accumulator, the Main Injector cycle time can be decreased substantially. • The reduction in Main Injector cycle time provides a 44% increase in 120 GeV beam power. • 2. The Recycler can also accommodate one more Booster batch than the Main Injector current does for slip stacking. • The extra batch would increase the beam power by 11%. Collider and Nova - McGinnis

  11. Planned Accelerator Upgrades for NoVa • 3. Once the collider is no longer running, the two antiproton production batches per Main Injector cycle can be allocated to the neutrino program • which yields another 20% increase in beam power. • 4.Upgrades to the Main Injector power system will permit a faster Main Injector energy ramp • yielding another 15% increase in beam power. • With these changes, the maximum Main Injector 120 GeV beam power will be 700kW. Collider and Nova - McGinnis

  12. Planned Accelerator Upgrades for NoVa Collider and Nova - McGinnis

  13. Proton Economics Run III - McGinnis

  14. Making Protons • To make lots of protons you need • longitudinal phase space • longitudinal phase space density • Making longitudinal phase space is easy but expensive. • This is why we chose the Recycler. • It has tons of longitudinal phase space and nobody else wanted it • So using it as proton accumulator is a "no-brainer". • Increasing longitudinal phase space density is • usually more difficult  • usually less expensive. Run III - McGinnis

  15. 120 GeV Beam Power Without the Recycler • As noted earlier, once the Recycler is re-commissioned for the NoVa program, it will be difficult to run Tevatron without a severe drop in luminosity. • By taking advantage of the otherNoVa upgrades to the Main Injector, it is possible • To keep the Recycler dedicated to the collider • And provide a 55-75% increase in Main Injector 120 GeV beam power over the present 320kW level Collider and Nova - McGinnis

  16. 120 GeV Beam Power Without the Recycler • 1. Faster Main Injector Cycle time yielding an 18% increase in beam power. • Faster ramps using the upgrades to the Main Injector power system • shorter flattop dwell times • eliminating deceleration energy ramp parabolas • 2. Allocate all of the currently available Proton Source Flux to NoVa and the collider programs • Stage 1. Increase the proton source batch intensity by 18% (11x1016 protons/hour – current Booster limit) • Stage 2. Increase the proton source batch intensity by another 13% (12.2x1016 protons/hour) • 3. Interleaving the antiproton production pulses to every other Main Injector ramp cycle will increase neutrino flux by 11%. Collider and Nova - McGinnis

  17. Proton Economics Collider and Nova - McGinnis

  18. Notes on Antiproton Production • The interleaving of antiproton production pulses reduces the proton flux on the antiproton production target • This would seem to cause a significant drop in the antiproton accumulation rate. • However, the antiproton source stochastic cooling becomes more efficient with the longer antiproton cycle time that would occur with interleaving. • Also since the antiproton uses only 10% of the proton source flux, • The proton source batch intensity for antiproton production can be increased substantially • With a negligible effect on the total proton flux. • The net reduction in antiproton stacking rate would be only 12%. Collider and Nova - McGinnis

  19. Tevatron Adjustments • The reduction of 12% in antiproton production rate would create a corresponding reduction in collider luminosity. • The reduction in luminosity can be compensated by increasing the number of protons at collisions. • To increase the number of protons at collision in the Tevatron, the Tevatron betatron tune working point would have to be moved. • The circuits for doing this are already in place. • The concept has been thoroughly worked out. • For implementation, study time would have to be allocated. Collider and Nova - McGinnis

  20. 120 GeV Beam Power Without the Recycler (Stage 1) • The 120 GeV beam power for Stage 1 would be 500kW which is 70% of the 700kW. • Stage 1 requires no additional cost beyond what is already allocated for NoVa • Stage 1 does not require the Proton Source to provide more flux than it currently is delivering. Collider and Nova - McGinnis

  21. Comments on Proton Flux • The Booster is the bottle-neck for proton flux at the Fermilab complex. • Hence the desire for Project X • The limit is set by beam loss and tunnel activation in the Booster • The maximum flux that the Booster has produced is 11x1016 protons/hour. • Which is where the Stage 1 limit is set. • No upgrades to the Booster for continued Tevatron running are required Collider and Nova - McGinnis

  22. Comments on Proton flux • To run higher beam powers to NoVa, the Proton source would have to provide more than 11x1016 protons/hour • The limit is set by beam loss and tunnel activation in the Booster • One of the main causes of beam loss is longitudinal emittance dilution. • There are two ways to combat this: • 1. More RF voltage (i.e more RF cavities) for bigger buckets • Straightforward solution • Expensive solution • 2. Reduce longitudinal emittance dilution • Better capture • Better damping • Space charge compensation with transverse phase space painting • These are cheaper cures – but more risky. Collider and Nova - McGinnis

  23. Comments on Proton Flux (continued) • There are many other projects that can be done in the Booster • More reliable RF power (solid state amplifiers) • Better Booster - MI cogging system (faster kickers) • Better orbit control (more ramp break points) • Bigger aperture (magnet moves) • Better tune control • Transverse dampers • Better longitudinal dampers (more bandwidth) • Better collimation (primary collimation) Collider and Nova - McGinnis

  24. Proton Economics Collider and Nova - McGinnis

  25. Summary • By taking advantage of the NoVa Upgrades to the Main Injector • it is possible to deliver at least 500kW of beam power to Nova • Without asking for more proton flux from the Booster than is currently available • Run the collider at the current level of luminosity Collider and Nova - McGinnis

  26. Booster Intensity Backup Slides Collider and Nova - McGinnis

  27. Main Injector Cycle Time • The NoVa upgrades to the Main injector is to install a new quad bus power supply and add two more RF stations. • This brings the cycle time to 1.33 seconds.  • The 1.33 second ramp includes • a 0.08 second 8 GeV dwell time • a 0.05 second flattop dwell time • two deceleration parabola's of 0.1 secs each.   • This accounts for  0.23 extra seconds • using only 1/2 of the parabola time • Looking at the regulation plots during the dwell times • the dwell times can be reduced • because there is plenty of bucket area at 120 GeV, flattop bunch rotation can be started during acceleration. • Also the deceleration parabola's can reduced or eliminated. • To go from 1.33 seconds to 1.2 seconds 0.13 seconds are eliminated by shortening the dwell times and deceleration parabola's.  Run III - McGinnis

  28. Slip Stacking Efficiency • The Booster longitudinal emittance and transverse emittance does not grow linear with intensity. • The Booster longitudinal emittance is dominated by instabilities • With the Booster longitudinal dampers, the longitudinal emittance is fairly flat over a wide range of intensity. • The slip stacking loss is from DC beam not captured in the in the final bucket. • This is a fairly intensity independent effect • no instabilities in the Main Injector • there is plenty of overhead in the RF power amplifiers for transient beam loading compensation. • Therefore slip stacking efficiency should be fairly constant with intensity Run III - McGinnis

  29. Booster Beam Intensity • The Booster routinely accelerates 5.3e12 with 93% efficiency for Tevatron fills • The efficiency for 4.3e12 is on the order of 94%. • To run 11e16 at 4.3 e12, the average Booster rep rate is 7.1Hz. • To run 500kW to NoVa, the Booster needs to run 5.1e12 at 5.9Hz. • This corresponds to a 15% increase in beam loss in the Booster tunnel. • Note that to do NoVa at 700kW, 27% more power is lost in the tunnel than is currently done at 11e16/hour.  • We assuming some improvement with • transmission increase with the new RFQ • higher RF voltage due to the reliability brought by the solid state RF upgrade. • Since there will have to be a lot of work done to get to 14e16/hour in the Booster, we are also assuming that Booster losses will decrease in the future. Run III - McGinnis

  30. Event $15 Operations Charge on shot to Tev. Intensity @ 5.25 and 93% efficient (No Notch on these cycles) Red is collimator loss Yellow is loss below BWT 5.0 3.0 4.0 1.5 3.0 0

  31. Antiproton Stacking Timeline • Since the Debuncher cooling is power limited • it is better to send a high intensity pulse at a slower cycle time • than a low intensity pulse at a short cycle time. • The scenario is to interleave stacking pulses every other Main injector ramp cycle. • For example, on Main Injector Cycle A, • 11 batches go to NoVa, • 0 go to pbar. • On Main Injector Cycle B, • 9 batches go to NoVa, • 2 go to pbar Run III - McGinnis

  32. Antiproton Stacking Rate • The Booster batch intensity for antiproton production goes from 4.5e12 to 5.5e12.  • The cycle time goes from the present 2.2 to 3.73 seconds. • This looks on surface like a 30% drop in flux. • The longer cooling time helps dramatically. • By increasing the cycle time to 3.73 seconds, the antiproton production efficiency should rise from 21e-6 to 30e-6 for the same number of protons on target. • Since the number of protons on target is increasing, the gain in production efficiency is de-rated the production to 26e-6. • Since the Debuncher cooling is power limited, this is a conservative estimate. • The Stacktail cooling system is in between power limited and gain limited, so the production of 26e-6 is justified Run III - McGinnis

  33. 5.6E12 @ 91% (No Notch) 6.0 Plot of Charge (green) Plot of loss at collimator (red) Plot of loss below BWT (yellow) 5.0 4.0

  34. The Tevatron • The change in working point concept • has been around for a long time since first pushed by Lebedev and Shiltsev. • has been thoroughly worked out by Valishev. • The luminosity integral is proportional to the number of protons. • Pushing the Tevatron tune closer to the 1/2 integer • as is done at the B-Factories • will give up to  50% more tune space than is currently obtained • which implies that the proton intensity can be increased by up to 50%. • We are asking to increase the proton intensity by 12%. • Complex luminosity evolution simulations • that takes into account emittances, long range effects, etc., • Showed that the luminosity integral lost by reduced stacking rate can be completely recovered. Run III - McGinnis

  35. Tevatron Working Point Scenarios Run III - McGinnis

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