Status of e production and trapping at Saclay

Status of e+ production and trapping at Saclay GBAR collaboration meeting Pierre Grandemange CNRS/CSNSM IRFU/SPP Saturday, September 26, 2020 Pierre Grandemange - CSNSM 1

Introduction Working at CEA Saclay for my Ph. D thesis on the positron trap from Riken 18 03 2012 Electron spot coming from the electron gun on a phosphor screen Several improvements have been made on positron production and accumulation experiment at CEA Saclay 26 September 2020 Pierre Grandemange - CSNSM 2

Plan 1. e+ production status 2. The improvements on the slow positron beamline 3. The RIKEN penning trap status 26 September 2020 Pierre Grandemange - CSNSM 3

e+ production Status at the last collaboration meeting * • • 10 Hz 140 m. A peak current 2. 5 µs effective pulse length Single W mesh moderator Ø ~1000 slow e+ / pulse ( 2 105 slow e+ / s ) *BGO counter lent by ETH Zurich laboratory 26 September 2020 Pierre Grandemange - CSNSM 4

e+ production Status today at the last collaboration meeting * • • 10 200 Hz Hz stable running 140 m. A peak current 2. 5 µs effective pulse length Single Multi-layers W mesh moderator Ø ~1000 3. 2 106 slow e+/se+ / pulse 5 ( 2 10 slow e+ / s ) Ø Comparable with the most intense 22 Na sources *BGO counter lent by ETH Zurich laboratory 26 September 2020 Pierre Grandemange - CSNSM 5

e+ production • • • Moderator (single 20 µm grid) was heated in situ by electrical current Slow positron yield monitored at the target Investigation of several developments Ø Chemical etching Ø Geometry Ø … • Present slow e+ rate 3. 2 106 s-1 Extrap. to 10 Me. V linac 4. 3 107 s-1 target value 2. 8 108 s-1 samedi 26 septembre 2020 • • Moderation efficiency decreases with temperature 30 minutes at 200 Hz : moderation efficiency reduced by 30% (Reversible) Still investigating long term effects Pierre Grandemange - CSNSM 6

e+ production • 11 -13 April : The Polish NCBJ Team has installed a new AFC Automatic Frequency Control - for the tuning of the Magnetron Ø Stability increased • The linac is stable enough for moderation development • The linac is stable enough to accumulate positrons in the trap • The linac energy will be monitored with the spectrometer installed by the NCBJ team samedi 26 septembre 2020 Pierre Grandemange - CSNSM 7

The improvements on the slow positron beamline Status at the last collaboration meeting Transmission : 91± 6% e- electron gun Tested in situ with e- and e+ Tested piece by piece with e. Not tested yet Linac e+ Magnetic field (Tesla) The beamline today ~45 Gauss 26 September 2020 Pierre Grandemange - CSNSM 8

The RIKEN penning-malmberg trap status Apparatus Magnetic field B = 5 Tesla Potential well V = 1 k. Volt Electron well length = 30 cm 26 September 2020 Pierre Grandemange - CSNSM 9

The RIKEN Penning-Malmberg trap status 0 -16 -100 -11 -6 -1 4 9 14 # electrode -200 Extraction -300 Signal on target -400 Extraction electrode -500 -600 -700 -800 Opened well for injection -900 Closed well -1000 Injection electrode Potential (V) 26 September 2020 Pierre Grandemange - CSNSM 10

The RIKEN Penning-Malmberg trap status Results with electrons Experimental Results at Riken 26 September 2020 Pierre Grandemange - CSNSM 11

The RIKEN Penning-Malmberg trap status Results with electrons • • 26 September 2020 Cool down the trap Apply the rotating wall technique Pierre Grandemange - CSNSM 12

The RIKEN Penning-Malmberg trap status 2. 1010 e- trapping easily reproducible Trap is now ready for positron trapping tests Fast High Voltage switch in development 26 September 2020 Pierre Grandemange - CSNSM 13

Thank you for your attention samedi 26 septembre 2020 Pierre Grandemange - CSNSM 14