1. JLEIC Accelerator R&D Meeting
Possibilities for Gear-Changing Experiments in Current and Future Colliders
Edward Nissen
JLEIC Accelerator R&D Meeting
11/2/2017

2. Gear changing via Path Length Change (e+e-) DaΦne Super KEK-B BEPC-II
Outline
Gear changing via Path Length Change (e+e-)
DaΦne
Super KEK-B
BEPC-II
Gear Changing via Inertia (ions)
NICA (future)
DESIREE
RHIC
Discussion
Possibilities for Gear-Changing Experiments in Current and Future Colliders 2

3. It is invasive, and would require a fair amount of engineering.
Gear Changing via path length
My assumption is that we would add a chicane to equal the bunch spacing in one of the rings, allowing for gear changing
It is invasive, and would require a fair amount of engineering.
Could only be done during long shutdowns
Well understood
If systematic error considerations are as important to the e+e- field as they are to the nuclear field they might be interested in developing the technology.
Possibilities for Gear-Changing Experiments in Current and Future Colliders 3

4. DAΦNE (Double Annular Φ factory for Nice Experiments)
Located at INFN Frascati
2 ~ 500 MeV beams, one e+ one e-
Up to 120 bunches in each ring at the same time
H+1 would require a pathlength change of ~ 80cm
Dense Lattice
Synchrotron radiation dominates the dynamics
The impedance budget might be blown with the addition of a chicane.
Possibilities for Gear-Changing Experiments in Current and Future Colliders 4

5. O(2500) bunches per ring with 7 on 4 GeV e+ e- collisions.
SUPERKEKB
At KEK in Tsukuba Japan.
O(2500) bunches per ring with 7 on 4 GeV e+ e- collisions.
H+1 pathlength change would be ~1.2 meters
Possibilities for Gear-Changing Experiments in Current and Future Colliders 5

6. Located in Beijing at IHEP Approximately 93 bunches per ring
BEPC-II (Beijing Electron Positron Collider II)
Located in Beijing at IHEP
Approximately 93 bunches per ring
Between 2 and 4.2 GeV center of mass e+ e- collisions
Path length difference of ~2.4 meters
Possibilities for Gear-Changing Experiments in Current and Future Colliders 6

7. Gear Changing via Inertia
Use different ion energies and species to create a velocity difference between two rings in a collider.
The lower energy will be the deciding factor in determining this “throw” between the two beams.
The lower energy can’t be more than 11 GeV/u or so (really 10.5) unless the machine is huge.
Hence the LHC is out.
Since this would require little to no change in the machine it should be as simple as running some simulations and getting some beam time.
Possibilities for Gear-Changing Experiments in Current and Future Colliders 7

8. Being built at JINR in Dubna Collides ions at 1-4.5 GeV/u
NICA (Nuclotron based Ion Collider fAcility)
Being built at JINR in Dubna
Collides ions at GeV/u
This energy difference allows a “throw” of 50.7 meters in a 454 meter collider ring with 22 bunches per ring.
Could actually test n on m instead of n(n-1)
Schedule currently unclear.
Possibilities for Gear-Changing Experiments in Current and Future Colliders 8

9. DESIREE (Double ElectroStatic Ion Ring ExpEriment)
Stockholm University facility
Ion beams from +/- 25 KeV to 100 KeV in either ring.
Bunch populations very low.
Would require using the different velocities to create collisions with a moving reference frame
Bunch populations are very low. O(106)
Interactions too weak for direct beam-beam experiments, but control and synchronization should be testable.
Low energy allows a lot of things not normally doable.
Possibilities for Gear-Changing Experiments in Current and Future Colliders 9

10. RHIC (Relativistic Heavy Ion Collider)
Brookhaven National Laboratory New York
RHIC is designed for asymmetric collisions, but the IR magnets are shared, so the rigidities must remain matched
Using the baseline numbers for RHIC a 28.4 GeV proton beam on a 10.8 GeV Gold beam would give a throw of 10.3 m which corresponds to 1 RF bucket.
Since RHIC only fills every third bucket a 15.5 GeV proton on 5.7 GeV Au scheme would be needed for gear changing. Both are higher than the lowest achieved operation.
Possibilities for Gear-Changing Experiments in Current and Future Colliders 10

11. Where N1 is the larger number
RHIC Experiment
Using data to the right, we can estimate the beam-beam tune shifts as follows for a hypothetical p on Au experiment:
Protons: ξ=
Gold: ξ=
According to the Hao et al. paper the stability criterion is that: ξ<(1/(4*N1))
Where N1 is the larger number
Assuming N1=120, the stability limit is
Possibilities for Gear-Changing Experiments in Current and Future Colliders 11

12. RHIC is the most promising machine.
Discussion
RHIC is the most promising machine.
Need to determine exact experiments.
DESIREE should be considered due to ease of use and low cost.
Low energy can allow a lot of things that are normally too difficult.
The e+e- colliders should still be considered if the systematics case is strong enough and there is interest in investigating the procedure.
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13. Thank You

14. Backup