Picnic Basket

Overview of the setup

Components installed

OAP1: 50.8 x 80.8mm EFL 28.1° Dielectric OAP https://drive.google.com/drive/folders/155hTVQilltHEs-FjaLeVUDGB8araIRcU

OAP1: 50.8 x 81.7mm EFL 30° Protected Gold OAP OAP1_datasheet.pdf  https://www.edmundoptics.com/p/508-x-762mm-pfl-30-off-axis-parabolic-gold-mirror/33465/

Modifications April 23-24, 2024: http://physics-elog.slac.stanford.edu/facetelog/show.jsp?dir=/2024/17/24.04&pos=2024-04-24T23:48:34

• Old M1 with burn mark in the middle from Axicon replaced with new one.

  old M1	new M1

• We changed the Gold OAP 1 to dielectric:

  Movable Focal spot camera	Laser level	Setup	Thickness difference

  Rotation angle set with level	marking at 8 mm from initial position (gold); wiped off  after the swap	Final position after shifting OAP mount backward by 8 mm	Dielectric OAP aligned

  • A movable camera placed at the focus and a laser level with crosshair on top edge of OAP 1 mount were used for alignment references.
  • The dielectric OAP is ~8 mm thicker than the gold. This difference is compensated using OAP 1 focal and horizontal picomotors. A spacer is added to the OAP 1 focal motor to extend its range.
  • The off-axis angle difference (28.1 vs 30) was compensated by parallel shifting of both OAP assembly and M2. New in positions are updated in confluence motor reference page.

  • Focal spot much improved (left: gold, right: dielectric):

    gold OAP focus after beamshaping	dielectric OAP focus after OAP optimization only

• We realigned M1-M2 closer to 90° to center the hole in the laser (left: before, right: after):

• The YAG target mount now has a new out position: 90 to prevent the picomotor from hitting the mounting plate.

Modifications December 13-19, 2022

• We changed the YAG (left: new, right: old):
• Currently installed:
  

Modifications November 2, 2022

• We installed a 6mm spacer below the MO tower
• We installed new external limit switches for the MO-tower and tested them
• We added an extension cable for the MO-tower TRA motor, such that it is now routed properly via the strain-release for the moving stage
• We improved the general cable management
• The picomotor for the vertical movement of OAP-1 needs to be replaced / cables need to be fixed.

MO imaging system outside the PB (November 2, 2022)

Modifications October 21, 2022

• We removed the two ~5mm spacers below the MO tower to lower the E-320 IP to the actual electron-beam height
• We (temporarily) took out the external limit switches for the MO-tower UTS stage (in/out): one of the two cables seems broken

Microscope Objective (information added 2022, June 21)

https://www.mitutoyo.com/webfoo/wp-content/uploads/E4191-378_010611.pdf

We are using the M Plan Apo NIR B 20x (https://www.edmundoptics.com/p/20x-mitutoyo-plan-apo-nir-b-infinity-corrected-objective/31874/), combined with a 300mm focal length lens for the large magnification camera (Email Zhijiang, June 21, 2022).

The collection angle of the objective is arcsin(0.4) = 23.58 degree (https://en.wikipedia.org/wiki/Numerical_aperture). As we are colliding at 30 degrees, the electron beam can clear the prism.

The prism in front of the MO is a 15mm Thorlabs right-angle prism with protective silver coating (https://www.thorlabs.com/thorproduct.cfm?partnumber=MRA15-P01). Prism dimensions were checked with ~1mm precision during the downtime 2022, June 20.

CeYAG installation June 20, 2022

Pictures from the E-320 setup

Target holder

(courtesy of Robert Ariniello)

Vacuum

• Low vacuum detection:
  VPTM:LI20:M3202:P full-range pirani gauge on the plasma oven turbo
  (valve 3201 has to be open)
  VGXX:LI20:3259:DS1:COMBO_P  the first stage of the differential pumping system
• Valve status: green (open) → EPICS reading "0", red (closed) → EPICS reading "1"