Photocathode Physics for Photoinjectors Workshop

12 Oct 2010, 08:30 → 14 Oct 2010, 14:00 US/Eastern

Instrumentation Division, Bldg. 535B, Room A-122 (Brookhaven National Laboratory)

Formulate photocathode requirements for photoinjectors (exclude polarization), review the state of the art, discuss the physics of photoemission, identify R&D directions to better understanding of photocathodes: review measurements (new data for thermal emittance, response time, etc.) and theory (better computer codes and modeling of photoemission), discuss new approaches and new materials, identify overlap and coordinate inter-laboratory efforts of mutual interests.

Tuesday, 12 October

Welcome (BNL Hosts)

Welcome (BNL Hosts)

Session 1 - Problem Formulation

Conveners: David Dowell (SLAC), Dr Triveni Rao (BNL)

1 Requirements for Photocathodes for Photoinjectors

30 min. talk/10 min. questions Extensive overview of requirements of the photocathodes, including specific requirements for pulsed FEL and high current ERL photoinjectors.

Speaker: David Dowell (SLAC)

Slides Cathode_Requirements_Dowell.pptx

2 Updates From Facilities: ANL, BNL, Cornell, JLAB, LBNL, European Labs, Japanese Labs

10 min. kicks off the discussion to follow. State what photocathodes are being worked on and for what application, existing equipment and capabilities. Each site to contribute 2 to 3 slides to the conveners.

Speaker: Triveni Rao (BNL)

document Copy_of_gun_performance_overview.xls

3 Discussion

Discussion charge: Update the table of requirements: pulsed versus high average current applications; table of available photocathode materials/labs with appropriate expertise; laboratory capabilities and techniques for photocathode characterization (including what's being planned and what's missing but would be nice to have).

Slides

• argonne_photocathodeRD.pdf
• Discussion_Photoemission_Emittance_PSI.ppt
• HZB_update_Schubert.ppt
• LBNL_photocathodes.ppt

10:30 15 min. Coffee Break

Session 2 - Measurement of Relevant Cathode Parameters

4 Alphabet Soup - An Overview of Materials Techniques

15 min. talk

Speaker: John Smedley (BNL)

Slides Alphabet_Soup_pdf.pdf

5 Cathode Recipes

15 min. talk

Speaker: Theodore Vecchione (LBL)

Slides Cathode_Recipes.pdf

6 In-Situ Diffraction

20 min. talk/10 min. questions

Speaker: Jean Jordan-Sweet (IBM)

Slides Photocathode_workshop_Jean_JordanSweet.pdf

12:30 In-room Lunch

7 Applications of Laser and Synchrotron Based ARPES to Photocathode Research

20 min. talk/10 min. questions

Speaker: Jon Rameau (BNL)

Slides Diamond_2010_Modern.pptx

8 Thermal Emittance; Response Time; Lifetime Measurements

20 min. talk/10 min. questions Overview of techniques, methods, limitations, etc. E.g. why some copper photocathode measurements report an emittance about x2 theory, while others basically agree with theory. Does this illuminate some error in thermal measurement?

Speaker: Luca Cultrera (Cornell Univ.)

Slides PPP2010-cultrera.ppt

9 In-Situ Quick Exafs

20 min. talk/10 min. questions

Speaker: Klaus Attenkofer (ANL)

Slides pc_xafs_short.pdf

10 Discussion

15:30 15 min. Coffee Break

11 MBE, ALD and XPS

30 min. talk/15 min. questions

Speaker: Scott Chambers (PNNL)

Slides Photocathode_workshop_Chambers.ppt

12 Discussion

Discussion charge: Proper measurement techniques of parameters relevant to accelerators; produce a list of measurement techniques that we can all agree on. Surface equipment/techniques available and desired for (to take most time). Photocathode growth and characterization. XPS, XRD, Topography, LEEM/PEEM, LEED/EBSD, SIMS, etc.--their application for understanding the structure and chemical form of the photocathodes, both initially and as a post mortum analysis. Substrate effects. New deposition techniques, such as ALD, with a focus on how they could help us grow better/more precisely engineered photocathodes. Product: Cathode recipe list

Slides

• BNL_P3_Workshop_ejm.ppt
• Greaves_Microdiffraction_Short_Talk_v2.ppt
• padmore_peem_v4.ppt
• QE_MAPPING_OF_A__CESIUM_DISPENSER__CATHODE-2.pdf
• TOF_ARPES_final_v2_greaves.ppt

Wednesday, 13 October

Session 3 - Photoemission Physics I: Theory

The first talks in this session provide a concise introduction into the subject, identify physics behind Spicer Model from Metals, then its extension to semiconductors, importance of the surface, and to provide the basis for physics carried on in Session 4.

13 Modeling of Photoemission

40 min. talk/5 min. questions To cover metals, antimonides, tellurides, NEA.

Speaker: Kevin Jensen (NRL)

Slides Jensen_PhotocathodePhysics.pdf

14 Physics of Semiconductor NEA Photocathodes

30 min. talk/5 min. questions

Speaker: Charles Sinclair (Cornell Univ.)

Slides Physics_of_NEA_Photocathodes.pptx

15 Photoemission Emittance

30 min. talk/5 min. questions

Speaker: John Schmerge (SLAC)

Slides Photo-emission.pptx

10:25 15 min. Coffee Break

16 Discussion

Discussion charge: Is 3 step Spicer model sufficient to explain practical photocathodes? If not, what are the limitations? pros/cons of each family--what knobs exist to tune the performance: QE vs. wavelength, better lifetime, faster response, lower thermal emittance; what physics parts are poorly understood and need a better theory effort; semiconductor properties needed for quantitative agreement with measurements, how to measure/calculate.

Slides B.L.Militsyn_3_slides_for_PPP2010.pptx Greaves__3_Step_Model_Short_Talk_v3.ppt

17 In-room Lunch

Session 4 - Photoemission Physics II: Agreement with Measurements

18 Multiscale 3D Simulations of Charge Gain, Transport, and Collection Efficiency in Diamond

30 min. talk/10 min. questions

Speaker: Dimitre Dmitrov (Tech-X)

Slides Dimitrov_P3_Workshop_BNL_Oct_Y10.pdf

19 Superlattice photocathode development for low emittance

30 min. talk/10 min. questions Model approaches and predictions, comparison with data, search for the optimal combination of thermal emittance and response time from NEA.

Speakers: Dr Makoto Kuwahara (Nagoya Univ.), Prof. Masahiro Yamamoto (KEK)

Slides BNL-kuwa.pdf PCWS2010BNL_MYamamoto.ppt

20 Hybrid Insulator/Semiconductor - Metals and CsBr Coatings

30 min. talk/10 min. questions

Speaker: Juan Maldonado (SLAC)

Slides BNL_workshop10-12-2010.ppt

21 Discussion

Discussion charge: What measurements are out there, what's missing; agreement of theory vs. existing measurements for a) QE vs. wavelength; b) thermal emittance; energy spectra; c) response time; identify (additional) conditions/requirements for controlled experiments for benchmarking with modeling.

15:30 15 min. Coffee Break

Thursday, 14 October

Session 5 - New Ideas and Future Collaborations

22 Plasmonic Interactions in Metallic Nanostructures

25 min. talk/5 min. questions

Speaker: Howard Padmore (LBL)

Slides Padmore_BNL_ppp_Oct_2010_v4.ppt

23 Multiphoton Emission

25 min. talk/5 min. questions MgF2 coated Cu Cathode for longer lifetime? Multiphoton photoemission from semiconductors? Anything else interesting from UCLA.

Speaker: Pietro Musumeci (UCLA)

Slides Musumeci_PPPworkshop.pptx

24 New Activation with K/Cs for Better Stability and Lifetime?

25 min. talk/5 min. questions

Speaker: Steven Sun (SLAC)

Slides 2010_10_LiCsNF3_PPP.ppt

25 Work Function Lowering and Ponderomotive E-Acceleration for Ultra Low Emittance Beams

25 min. talk/5 min. questions

Speaker: Karoly Nemeth (ANL)

Slides Photocathode-BNL-2010-Oct-14-2010-1_Nemeth.pdf

10:30 15 min. Coffee Break

26 Discussion

Discussion charge: Manufacturer's/lab's capabilities with regards to new material growth; sharing resources for a) photocathode prep recipes; b) measurement equipment. User facilities for photocathode research (e.g. to measure thermal emittance/response time). Testing of materials in the actual photoguns. Discussion on the repository.

document Photocathode_Catalog.xlsx

Slides Future_of_P3_v2.pptx p3workshop@cornell.ppt

27 Adjourn

28 BNL Facilities Tours