Ion channel wiggler Zulfikar Najmudin, Savio Rozario , Rob Shalloo , John Wood

1. Ion channel wigglerZulfikar Najmudin, Savio Rozario, Rob Shalloo, John Wood ATF User Meeting 14-11-2018 Z. Najmudin

2. Scientific Case Kneip, S. et al.Nat. Phys. 6, 980–983 (2010). Cole, J. M. et al. Proc. Natl. Acad. Sci., 2018/06/04/1802314115

3. Scientific Case Ion channel can be produced by either intense particle or laser beam At ne ≈ 1017 cm-3, Ey ≈ 1011 Vm-1 (∼ B≈300 T) 𝜆𝛽≈1.8 mm, zR ≈ 3 mm ⇾ guiding desirable 𝜔c ≳ 1000 𝜔0 ⇾ radiation in UV Whittum D.et al.Phys. Rev. Lett.64, 2511 (1990).

4. Experimental Setup

5. Plans – Guided propagation At P/Pcr> 1, pulse prone to instabilities ⇾ guiding channel desirable Try to keep a0 <1, but big channels preferable ⇾ only CO2 laser suitable Could potentially use hydrodynamically formed channels

6. Hydrodynamic channels • On Axis Density vs Fill Pressure • HOFI Plasma Channel Expansion • 50μm • Plasma Parameters • Plasma waveguides formed in H2 • Low On-Axis densities ~ 1017 cm-3 • Matched Spot Sizes ~ 10’s microns • Laser Parameters • Low-energy required: 10-70 mJ @ 50 fs • Formed with Lens or Axicon R. J. Shalloo, C. Arran et. al. , Phys. Rev. E, 97 053203 (2018)

7. Radiation from ion channels Radiation from channel guided electrons observed on Vulcan PW Strongest radiation observed when electrons experience large transverse kicks due to DLA Kneip, S. et al. Observation of Synchrotron Radiation from Electrons Accelerated in a Petawatt-Laser-Generated Plasma Cavity. Phys. Rev. Lett. 100, 105006 (2008).

8. Plans • Experiment waiting for laser and electron beam upgrades, and new appointments. • First experiment to test laser beam guiding – can we make hydrodynamic channels? • Secondary goal will be to co-propagate electron beam, and measure its betatron motion as function of gas cell length. • New gas cell being developed to allow variable length • Second period would concentrate on radiation detection

9. Electron Beam Requirements • Special Equipment: • Please indicate any special equipment that you expect to need, including (but not limited to) the transverse deflecting cavity, shaped bunch using mask technique, plasma capillary discharge system, bolometer/interferometer setup etc.

10. CO2 Laser Requirements The following options are available at the laser source. Note that the maximum power available at your experiment interaction point will depend on the laser transport method. OPTION 1 (full power, ~1 shot per minute)isotopic gas in final amplifier2 TW max (2 ps, 4 J, single pulse)Need relaxed focussing ~ 100 µm – a0 ~ 1 would be desirableM^2 ~2linear polarizationWould like secondary beam for forming hydrodynamic channels (either ps YAG or fs Ti:sapphire) Would like to try to probe interaction with secondary beam too. ** Please note any specialty laser configurations here ** Interaction Point location: Laser room/electron experiment hall - delete as necessary (the highest peak power can be delivered to the laser room chamber and 2 beamline #1 chambers. CO2 laser delivery to beamline #2 will see lower power due to necessary transport in air.)

11. 2019 Experiment Time Estimates Run Hours (include setup time in hours estimate): Number of electron beam only hours: 0 Number of CO2 laser hours delivered to laser experiment hall (”FEL room”): 50 Number of CO2 laser hours, + ebeam, delivered to electron beam experiment hall: 50 Overall % setup time: 50% Hazards & installation requirements: Large installation (chamber, insertion device etc…): N Laser use (other than CO2): Y Cryogens: N Introducing new magnetic elements: Y? Introducing new materials into the beam path: N Any other foreseeable beam line modifications: N Please describe further where necessary