A First Brief Report on Bunched Beam Electron Cooling Experiment at IMP, China Click to add title Click to add subtitle Tom Powers, Haipeng Wang, He Zhang and Yuhong Zhang JLEIC Accelerator R&D Meeting, June 2 2016 JLEIC R&D Meeting 2/25/16

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

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

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

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

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