Title: Modeling quantum yield, emittance, and surface roughness effects from metallic photocathodes

Abstract

Here, detailed measurements of momentum distributions of emitted electrons have allowed the investigation of the thermal limit of the transverse emittance from metal photocathodes. Furthermore, recent developments in material design and growth have resulted in photocathodes that can deliver high quantum efficiency and are sufficiently robust to use in high electric field gradient photoinjectors and free electron lasers. The growth process usually produces photoemissive material layers with rough surface profiles that lead to transverse accelerating fields and possible work function variations, resulting in emittance growth. To better understand the effects of temperature, density of states, and surface roughness on the properties of emitted electrons, we have developed realistic three-dimensional models for photocathode materials with grated surface structures. They include general modeling of electron excitation due to photon absorption, charge transport, and emission from flat and rough metallic surfaces. The models also include image charge and field enhancement effects. We report results from simulations with flat and rough surfaces to investigate how electron scattering, controlled roughness, work function variation, and field enhancement affect emission properties. Comparison of simulation results with measurements of the quantum yield and transverse emittance from flat Sb emission surfaces shows the importance of including efficient modeling ofmore » photon absorption, temperature effects, and the material density of states to achieve agreement with the experimental data.« less

Authors:

Dimitrov, D. A. ^[1]; Bell, G. I. ^[1]; Smedley, J. ^[2]; Ben-Zvi, I. ^[2]; Feng, J.  ^[3];

• Search DOE PAGES for author "Feng, J."
• Search DOE PAGES for ORCID "0000-0002-5292-8842"

Karkare, S.  ^[4];

• Search DOE PAGES for author "Karkare, S."
• Search DOE PAGES for ORCID "0000-0002-7759-0032"

Padmore, H. A. ^[3]

---

+ Show Author Affiliations

1. Tech-X Corp., Boulder, CO (United States)
2. Brookhaven National Lab. (BNL), Upton, NY (United States)
3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); UCLA, Los Angeles, CA (United States)

Publication Date:

Thu Oct 26 00:00:00 EDT 2017

Research Org.:

Tech-X Corp., Boulder, CO (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Nuclear Physics (NP)

OSTI Identifier:

1406895

Alternate Identifier(s):

OSTI ID: 1405044; OSTI ID: 1412775

Report Number(s):

BNL-114790-2017-JA
Journal ID: ISSN 0021-8979; TRN: US1703044

Grant/Contract Number:  

SC0015767; SC0013190; SC0012704

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Applied Physics

Additional Journal Information:

Journal Volume: 122; Journal Issue: 16; Journal ID: ISSN 0021-8979

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; 43 PARTICLE ACCELERATORS