1. A First Brief Report on Bunched Beam Electron Cooling Experiment at IMP, China
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Tom Powers, Haipeng Wang, He Zhang and Yuhong Zhang
JLEIC Accelerator R&D Meeting, June
JLEIC R&D Meeting
2/25/16

2. What Had Happened at IMP?
Preparation before the experiment
IMP colleagues built a high voltage power supplier platform (the old one is custom-build by Russians, with out-dated electronics)
JLab staffs (T. Powers, K. Jordan) built a pulsed RF power supplier for the thermionic gun grid and shipped/installed to the IMP cooler; they also wrote a control software for the pulsar (RF frequency and amplitude)
Conducting the experiment
IMP allocated 7 days (2.5 days for start-up of the storage ring and 4.5 days for measurements)
Due to the hardware issue, the previous experiment was extended for 2 days, this experiment has a late started and was also extended for 1 day
Both experiments (pulsed beam cools a coasting beam and a bunched beam), Ion energy is 7 MeV/u, and ion species is Cabon
Both IMP staffs and JLab staffs (T. Powers, H. Zhang and Y. Zhang) participated the experiment.
JLEIC R&D Meeting
2/25/16

3. What Had Been Tested? What We had Observed? What We Believe Understood?
Test 1: Long pulsed (~5 µs) electron beam cools a coasting ion beam, two beams were not synchronized
We observed a rapid ion loss in very short time
Ion loss was too fast that cooling effect could not be observed
We suspect that the raise/fall of pulsed electron beam acted as a transverse kicker which knocks out the ions piece-by-piece
We also suspect that the electron beam and ion beam are not perfectly aligned
Test 2: Long pulsed electron beam cools a coasting ion beam, two beams were synchronized
We observed a modest to small ion loss
We observed a rapid cooling effect (longitudinal cooling)
We suspect that the raise/fall of pulsed electron beam acted as a transverse kicker which knocks out the ions only in two specific locations
JLEIC R&D Meeting
2/25/16

4. What Had Been Tested? What We had Observed? What We Believe Understood?
Test 3: Long pulsed (~2 µs) electron beam cools a bunched ion beam, two beams were synchronized
Only one of two ion bunches were cooled (seeing electrons)
Electron bunches is longer than the ion bunches
We observed a small ion loss
We observed cooling effect (longitudinal cooling)
We suspect that the raise/fall of pulsed electron beam did not see ions so no ions were kicked out
Test 4: Pushing Short pulse length of electron beam and use it to cool a coasting ion beam, two beams were synchronized
We pushed the electron bunch length (FWHM) down as short as 100 ns (about 6 m)
No cooling were observed with electron bunch short than 150 ns (~9 m); we suspect that longitudinal diffusion is too slow (ineffective) to spread cooling along the coasting beam
With a little longer electron pulse length, we observed cooling effect.
At 400 ns pulse length, ions were lost rapidly which could not be explained. We suspected the ion beam had hit some instability
We observed a likely bunching effect in the ion beam by cooling (through existing two side bends
JLEIC R&D Meeting
2/25/16

5. Archiving and Analyses of Experimental Data, and Comparison with Simulations
Collecting and archiving of the experimental date
Tom brought back 8 GB data; there were more data in IMP which will be transferred to JLab
Analyses of the experimental date has just began
An IMP graduate student of Lijun Mao has completed a preliminary analyses of part of the first day date; They have been fitted with a double-Gaussian mode
Simulations of Ion Beam Bunching effect due to bunched beam cooling
Both Youjin Yuan of IMP and He Zhang of JLab had performed a simulation to demonstrate this grouping/bunching effect
He Zhang’s simulation has to boost the electron cooling beam current to amplify this effect to be visible during cooling
JLEIC R&D Meeting
2/25/16

6. What Are Next Steps?
Continue to analyses the experimental date to get full physics out
Will be done by the collaboration team, staffs from both institutions
It likely will take several weeks to two months
After that, we need to decide whether we have enough physics results for a publication
If not, what additional test needs to be done to make up
Will continue to do simulations
For comparison with experimental data and for code benchmark
We definitely need to improve the capabilities of the pulsar and beam diagnostics
Adjusting frequency and change the pulse shape for parameter dependence study
Exploring possibility for testing at higher energy
JLEIC R&D Meeting
2/25/16