TABLE I.

Simulated temporal spread of electron bunches with different initial states and instrumental conditions. The guard ring cathode was positioned both at 750 μm and 500 μm gaps, the truncated tip cathode at 650 μm, and ΔE_i is the initial energy spread.

Case No.	ΔEi (eV)	Angle distribution	Electron emission spatial distribution	Δt (Bias 50 V)			Δt (Bias 650 V)
				Guard ring cathode (750 μm)	Guard ring cathode (500 μm)	Truncated tip cathode (650 μm)	Guard ring cathode (750 μm)	Guard ring cathode (500 μm)	Truncated tip cathode (650 μm)
1	0.8	Lambertian	Gaussian	1.4 ps	0.7 ps	0.7 ps	8.0 ps	1.2 ps	6.4 ps
2	0.8	Normal	Gaussian	1.0 ps	0.6 ps	0.6 ps	6.0 ps	0.9 ps	4.9 ps
3	0	Lambertian	Gaussian	1.1 ps	0.6 ps	0.7 ps	5.1 ps	0.9 ps	4.6 ps
4	0	Normal	Gaussian	0.3 ps	0.3 ps	0.4 ps	0.9 ps	0.3 ps	1.5 ps
5	0.8	Lambertian	Central point	1.3 ps	0.7 ps	0.6 ps	7.7 ps	1.1 ps	6.1 ps