1. March 28-April, 2011 2011 Particle Acceleratior Conference - New York, U.S.A. Comparison of back-scattering properties of electron emission materials Abstract  Monte Carlo (MC) simulations and empirical theories were applied to identify the influence of back-scattered electrons and the saturation effect on the emissive properties of materials and to study the gain and transit times for various microchannel plates (MCPs).  Al 2 O 3 and MgO of various thickness and surface quality were studied.  SEY, BS data were calculated at oblique angles of the primary electrons in the interval of 0-80 .  SEY, BS data were submitted to our trajectory simulation MC code which is capable of gain and transit time calculations.  The deposition and characterization experiments were conducted for the Large Area Picosecond Photodetector project at Argonne National Laboratory. Motivation Table 1. Material parameters for MC simulations Back-scattered electron coeficinets of Al 2 O 3 SEY and BSC of Al 2 O 3 MCP Gain and Transit time simulations  Our MCP simulation takes into account the saturation effect [1] and backscattered electrons.  A single MCP of 1.2 mm thickness with 20 μm pores, 8° bias angle, 1 kV applied MCP voltage was used.  The energy of incoming photo electrons: 350 eV.  Gain was calculated for each cascade of secondary electrons.  Arrival time (AT) (the time when the MCP pulse crosses 10% of the pulse max) was averaged over the number of pulses.  Table 2 and Fig. 5 present the results for true secondary (TS) emission only and for both TS and back- scattering (BS) electrons with different angular bins (ABs) representing the SEY data given in Figs. 1-4.  These results show that the contribution of the back- scattering electrons should have a significant impact on the total MCP gain and a discernible effect on the transit time of the MCPs.  Future studies are needed to compare device-level MCP measurements with MCS simulations for different materials.  These studies will help researchers better understand the role of back- scattering and help constrain our models.  Theoretical studies of secondary electron emission yields (SEYs) are necessary as a preliminary step in developing new emissive materials for particle detectors based on microchannel plates (MCPs) in high-energy physics, such as Cherenkov, neutrino, and astroparticle detectors.  Secondary electrons also play a significant role in the development of new scanning electron microscopes.  The back-scattering electrons can make a substantial contribution to the total MCP gain and can alter the transit time.  To our knowledge, BSC contributions to gain and transit times were not taken into account so far. Acknowledgements Introduction  The goal of this work is to develop a parameterized set of the SEY dependencies in two variables: the energy of the primary electron and the angle of incident electrons for Al 2 O 3 and MgO that are of interest for collaboration in the Large-Area Picosecond Photodetector (LAPD) project at Argonne National Laboratory.  This parameterization can be done by using results obtained from Monte Carlo (MC) micro scale calculations.  The transit time, gains and spatial resolution critical for the new LAPDs have not been available with the conventional glass MCPs.  The new MCP concept is based on micron-scale pores fabricated in alumina by Atomic Layer Deposition method. Secondary electron emission and backscattered yields Pulse-hight distribution with (red) and without (line) backscattered electrons Summary Z. Insepov, V. Ivanov, S. Jokela, M. Wetstein Argonne National Laboratory, Argonne, IL USA Material , eV  Å Al 2 O 3 27.520 MgO 20120 The secondary emission yield (SEY) (Fig.1,3) were obtained for Al 2 O 3 and MgO by MC calculations with the adjustable parameters from literature. The alumina data for normal incidence, 45  and 80  were chosen to match the input used by the CASCADE code developed at Arradiance company (Fig.1). Backscattering coefficients of both materials were calculated by the CASINO MC code (Fig. 2,4). The values of  m and E m at various incidence angles were obtained by a smooth interpolation of the appropriate SEY and E values for the CASCADE yields. Simulation CodeBinsGainAT, ps MCS (Argonne code) (True SE only) 10 21,300348 MCS (Argonne code) (TS+BS) 10 60,700362 (Eq. 1) MCP simulations with saturation Table 2. Gain, AT simulations Pulse Height Distributions Fringe fields simulations in 3D Model of charge saturation Geometry of saturation models A. Spherical symmetry z r r = 10 nm Al 2 O 3 +ZnO Primary electron SEE r rr z r = 20  m  r = 10 nm Aspect ratio 60 B. Cylindrical symmetry SEY, BSC data were used for MCP gain and transit time simulations that simulates avalanche inside an MCP pore. The feedback from the gain code was used to stimulate further search for better MCP materials. Fig. 1 Experimental BSCs of Al Fig. 2 Fig. 3Fig. 4 This work was supported by the Office of Science, under Contract DE-AC02- 06CH11357. Fig. 5 COMSOL simulationsMCP trajectory simulations