Absolute Beam Energy
Jump to navigation
Jump to search
Summary Table
Table 1 <ref name="Dowell"/>
Properties of metal photocathodes.
| Metal Cathodes | Wavelength & Energy: λopt (nm), ℏω (eV) | Quantum Efficiency (electrons per photon) | Vacuum for 1000h operation (Torr) | Work Function, φw (eV) | Thermal Emittance (microns / mm(rms)) Eq. (1) | Thermal Emittance (microns / mm(rms)) Expt. |
|---|---|---|---|---|---|---|
| Bare Metal | ||||||
| Cu | 250, 4.96 | 1.4 x 10-4 | 10-9 | 4.6 <ref name="Sommer1"/> | 0.5 | 1.0 ± 0.1 <ref name="Graves"/> |
| 1.2 ± 0.2 <ref name="Schmerge"/> | ||||||
| 0.9 ± 0.05 <ref name="Ding"/> | ||||||
| Mg | 266, 4.66 | 6.4 x 10-4 | 10-10 | 3.6 <ref name="Michaelides"/> | 0.8 | 0.4 ± 0.1 <ref name="Michaelides"/> |
| Pb | 250 , 4.96 | 6.9 x 10-4 | 10-9 | 4.0 <ref name="Sommer1"/> | 0.8 | ? |
| Nb | 250 , 4.96 | ~2 x 10-5 | 10-10 | 4.38 <ref name="Sommer1"/> | 0.6 | ? |
| Coated Metal | ||||||
| CsBr:Cu | 250 , 4.96 | 7 x 10-3 | 10-9 | ~2.5 | ? | ? |
| CsBr:Nb | 250 , 4.96 | 7 x 10-3 | 10-9 | ~2.5 | ? | ? |
The thermal emittances are computed using the listed photon and work function energies in Eq. (1) and express the thermal emittance as the normalized rms emittance in microns per laser size in mm. The known experimental emittances are given with references.
Table 2 <ref name="Dowell"/>
Properites of semiconductor cathodes.
| Cathode Type | Cathode | Typical Wavelength & Energy, λopt (nm), (eV) | Quantum Efficiency (electrons per photon) | Vacuum for 1000 h (Torr) | Gap Energy + Electron Affinity, EG+EA (eV) | Thermal Emittance (microns / mm(rms)) Eq. (2) | Thermal Emittance (microns / mm(rms)) Expt. |
|---|---|---|---|---|---|---|---|
| PEA: mono-alkali | Cs2Te | 211, 5.88 | 0.1 | 10-9 | 3.5 <ref name="Sommer2"/> | 1.2 | 0.5 ± 0.1 <ref name="Sertore"/> |
| 262, 4.70 | - | - | " | 0.9 | 0.7 ± 0.1 <ref name="Sertore"/> | ||
| 262, 4.73 | - | - | " | 0.9 | 1.2 ± 0.1 <ref name="Miltchev"/> | ||
| Cs3Sb | 432, 2.87 | 0.15 | ? | 1.6 + 0.45 <ref name="Sommer2"/> | 0.7 | ? | |
| K3Sb | 400, 3.10 | 0.07 | ? | 1.1 + 1.6 <ref name="Sommer2"/> | 0.5 | ? | |
| Na3 | 330, 3.76 | 0.02 | ? | 1.1 + 1.6 <ref name="Sommer2"/> | 0.4 | ? | |
| Li3Sb | 295, 4.20 | 0.0001 | ? | ? | ? | ? | |
| PEA: multi-alkali | Na2KSb | 330, 3.76 | 0.1 | 10-10 | 1 + 1 <ref name="Sommer2"/> | 1.1 | ? |
| (Cs)Na3KSb | 390, 3.18 | 0.2 | 10-10 | 1 + 0.55 <ref name="Sommer2"/> | 1.5 | ? | |
| K2CsSb | 543, 2.28 | 0.1 | 10-10 | 1+1.1 <ref name="Sommer2"/> | 0.4 | ? | |
| 532 | 0.56 ± 0.03 <ref name="Bazarov3"/> | ||||||
| K2CsSb(O) | 543, 2.28 | 0.1 | 10-10 | 1 + <1.1 <ref name="Sommer2"/> | ~0.4 | ? | |
| NEA | GaAs(Cs,F) | 532, 2.33 | 0.1 | ? | 1.4 ± 0.1 <ref name="Sommer2"/> | 0.8 | 0.44 ± 0.01 <ref name="Bazarov1"/> |
| 860, 1.44 | 0.1 | ? | 0.2 | 0.22 ± 0.01 <ref name="Bazarov1"/> | |||
| GaN(Cs) | 260, 4.77 | 0.1 | ? | 1.96 + ? <ref name="Bazarov1"/> | 1.35 | 1.35 ± 0.1 <ref name="Bazarov2"/> | |
| GaAs(1-x)Px x~0.45 (Cs,F) | 532, 2.33 | 0.1 | ? | 1.96 + ? <ref name="Bazarov1"/> | 0.49 | 0.44 ± 0.1 <ref name="Bazarov1"/> | |
| S-1 | Ag-O-Cs | 900, 1.38 | 0.01 | ? | 0.7 <ref name="Sommer2"/> | 0.7 | ? |
The thermal emittances are computed using the listed photon, gap and electron affinity energies in Eq. (2) and express the thermal emittance as the normalized rms emittance in microns per rms laser size in mm.