Note: Simulation and test of a strip source electron gun Munawar Iqbal, G. U. Islam, I. Misbah, O. Iqbal, and Z. Zhou Citation: Review of Scientific Instruments 85, 066106 (2014); doi: 10.1063/1.4883175 View online: http://dx.doi.org/10.1063/1.4883175 View Table of Contents: http://scitation.aip.org/content/aip/journal/rsi/85/6?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Generation and focusing of electron beams with initial transverse-longitudinal correlation J. Appl. Phys. 116, 133302 (2014); 10.1063/1.4897227 Determination of the ReA Electron Beam Ion Trap electron beam radius and current density with an X-ray pinhole camera Rev. Sci. Instrum. 85, 073302 (2014); 10.1063/1.4885448 A novel electron gun for inline MRI-linac configurations Med. Phys. 41, 022301 (2014); 10.1118/1.4860660 Development of electron beam ion source charge breeder for rare isotopes at Californium Rare Isotope Breeder Upgradea) Rev. Sci. Instrum. 83, 02A902 (2012); 10.1063/1.3660823 The Brookhaven National Laboratory electron beam ion source for RHICa) Rev. Sci. Instrum. 81, 02A509 (2010); 10.1063/1.3292937
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REVIEW OF SCIENTIFIC INSTRUMENTS 85, 066106 (2014)
Note: Simulation and test of a strip source electron gun Munawar Iqbal,1,2,a) G. U. Islam,1 I. Misbah,1 O. Iqbal,1 and Z. Zhou2 1 2
Centre for High Energy Physics, University of the Punjab, Lahore 45590, Pakistan Institute of High Energy Physics, Chinese Acedemy of Sciences, Beijing 100049, China
(Received 2 December 2013; accepted 1 June 2014; published online 11 June 2014) We present simulation and test of an indirectly heated strip source electron beam gun assembly using Stanford Linear Accelerator Center (SLAC) electron beam trajectory program. The beam is now sharply focused with 3.04 mm diameter in the post anode region at 15.9 mm. The measured emission current and emission density were 1.12 A and 1.15 A/cm2 , respectively, that corresponds to power density of 11.5 kW/cm2 , at 10 kV acceleration potential. The simulated results were compared with then and now experiments and found in agreement. The gun is without any biasing, electrostatic and magnetic fields; hence simple and inexpensive. Moreover, it is now more powerful and is useful for accelerators technology due to high emission and low emittance parameters. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4883175] Indirectly heated strip cathode produces high beam currents and heating efficiency. Moreover, the practical heating temperature can be maximized and the thermal run away could be avoided.1 These guns are highly useful for melting and evaporation of refractory metals and for accelerators technology,2 due to high thermal load and long duty cycles. This is because of large surface area of the strip which serves as the source of electrons continuously. Some recent developments on this particular geometry have been reported in the literature.3–5 In continuation to our developments6–11 on electron guns, we have simulated the strip source electron gun for maximum practical emission current density and beam convergence in the post-anode region by computing charged particle trajectories using Stanford Linear Accelerator Center (SLAC) EGUN software.12 This is possible only if we focus the beam in a small area to the order of few millimeters. A detailed design and test of the assembly has been reported earlier in the same journal;10 hence, used the same spatial and voltage parameters for the simulation. A detailed diagram of the assembly is given in Figure 1. The geometrical parameters fixed for beam optimization are listed in Table I. Finally, simulations were compared with the experiments for then and now results. Potentials applied to different electrodes are given in Table II. Therefore, the obtained electron beam trajectories for the actual configuration are shown in Figure 2. The beam was not converged to a single point due to scattering in the post anode region. This measurement is compatible with Ref. 10, where we could not obtained any beam at the target, though 600 mA beam current was recorded at the output. Whereas, the trajectories for the optimized configuration given in Figure 3 exhibited that beam was focused in the post anode region at 15.9 mm where its diameter was measured to be 3.04 mm.
Emission current densities as a function of beam radius for the both configurations are shown in Figure 4. These profiles are plot normalized to 1.0 (with the peaks, as shown at the top of both plots); with values of maximum emission current density equal to 0.31 A/cm2 for the actual and 9.28 A/cm2 for the optimized configuration. The average values for these emission current densities were 0.063 A/cm2 and 1.15 A/cm2 , respectively. We also calculated average values of power densities for both configurations and obtained 0.63 kW/cm2 and 11.5 kW/cm2 for actual and optimized configurations, respectively. Figure 5 shows the phase space plot of two configurations, from which the emittance can be understood. A good convergent beam, with low emittance and no aberrations would have all the points lying in a straight line.12 We found total emittance 460.5 and 208.8 π mm mrad for the actual and the optimized configurations, whereas the normalized values were 91.56 and 41.5 π mm mrad, respectively.
a) Author to whom correspondence should be addressed. Electronic mail:
FIG. 1. Reprinted with permission from Rev. Sci. Instrum. 74, 1196, (2003). Copyright 2003 American Institute of Physics.
[email protected].
0034-6748/2014/85(6)/066106/3/$30.00
85, 066106-1
© 2014 AIP Publishing LLC
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066106-2
Iqbal et al.
Rev. Sci. Instrum. 85, 066106 (2014)
TABLE I. Parameters fixed for beam optimization.
Parameters
Actual gun configuration (mm)
Optimized gun configuration (mm)
... 6.0 ... ... 15
6.1 8.5 2.4 13.35 13.4
Cathode to focusing electrode distance Cathode to anode distance Focusing electrode to anode distance Focusing electrode slit spacing Anode hole diameter
TABLE II. Potential applied to electrodes for the two configurations. Electrodes Cathode (kV) Focusing electrodes (kV) Anode (kV)
Actual gun
Optimized gun
−10 ... −4
−10 −10 0
FIG. 4. Current densities as a function of beam radius.
FIG. 2. Beam trajectories of the actual gun. FIG. 5. Phase space profiles of the both configurations
TABLE III. Emission parameters of the both configurations.
Parameters
Actual configuration
Optimized configuration
Beam diameter (mm) Beam focusing distance from anode (mm) Beam current (mA) Maximum current density (A/cm2 ) Average current density (A/cm2 ) Power density (kW/cm2 ) Total emittance (π mm mrad) Normalized emittance (π mm mrad)
Not focused Not focused 600 0.31 0.063 0.63 460.5 91.56
3.04 15.9 1120 9.28 1.15 11.5 208.8 41.5
FIG. 3. Beam trajectories of the optimized gun.
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066106-3
Iqbal et al.
Rev. Sci. Instrum. 85, 066106 (2014) TABLE IV. Measured results of the optimized design. Parameters Beam cross section (mm2 ) Beam current (mA) Current density (A/cm2 ) Power density (kW/cm2 ) Target distance from anode (mm)
FIG. 6. Measured beam profile at the SS target.
Values 3.15 × 35 1120 1.02 10.2 15.9
ble size of the length of the source. The beam current has been increased to more than 90%. The gun is now more powerful for refractory metals evaporations and has enhanced features for the use of accelerator technology due to high emission and low emittance of the beam. 1 J.
A summary of comparison of emission characteristics of both configurations of the gun is shown in Table III. Finally, the gun was tested experimentally by placing a SS target at the optimized distance (15.9 mm) in the post anode region. Figure 6 shows the beam profile obtained with 1120 mA beam current; has 3.15 × 35 mm2 cross section of the beam at the target. The measured current density for this profile was 1.02 A/cm2 that corresponds to power density 10.2 kW/cm2 , hence, confirmed the compatibility between the simulated and experimental results. After optimization of the gun, the experimentally measured results mentioned above are summarized in Table IV below. Thus, with the help of simulation by EGUN, we were able to determine the emission characteristics of the gun. The gun has been focused sharply at the target with the compara-
Yeheskel, D. Gazit, R. Avida, and M. Friedman, J. Phys. D 16, 499 (1983). 2 Z. Zhou and L. Bo, Chin Phys. C 29, 1196 (2005). 3 N. Maiti, K. Lijeesh, U. D. Barve, N. Quadri, G. U. Tembhare, S. Mukherjee, K. B. Thakur, and A. K. Das, Rev. Sci. Instrum. 84, 083302 (2013). 4 N. Maiti, S. Mukherjee, B. Kumar, U. D. Barve, V. B. Suryawanshi, and A. K. Das, Rev. Sci. Instrum. 81, 013302 (2010). 5 S. Mukherjee, N. Maiti, U. D. Barve, and A. K. Das, Vacuum 84, 920 (2010). 6 M. Iqbal, G. U. Islam, S. Saleem, and W. B. Herrmannsfeldt, Vacuum 101, 157 (2014). 7 M. Iqbal, G. U. Islam, Z. Zhou, and Y. Chi, Rev. Sci. Instrum. 84, 116107 (2013). 8 M. Iqbal, A. Wasy, and M. A. K. Lodhi, Rev. Sci. Instrum. 84, 056113 (2013). 9 M. Iqbal and F. Aleem, Rev. Sci. Instrum. 77, 106101 (2006). 10 M. Iqbal, M. A. Chaudhary, M. Rafiq, K. Masud, and F. Aleem, Rev. Sci. Instrum. 74, 1196 (2003). 11 M. Iqbal, K. Masud, M. Rafiq, M. A. Chaudhary, and F. Aleem, Rev. Sci. Instrum. 74, 4616 (2003). 12 W. B. Herrmannsfeldt, SLAC-331-UC-28, 1 (1988).
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 132.206.7.165 On: Thu, 11 Dec 2014 17:16:04
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 132.206.7.165 On: Thu, 11 Dec 2014 17:16:04
REVIEW OF SCIENTIFIC INSTRUMENTS 85, 066106 (2014)
Note: Simulation and test of a strip source electron gun Munawar Iqbal,1,2,a) G. U. Islam,1 I. Misbah,1 O. Iqbal,1 and Z. Zhou2 1 2
Centre for High Energy Physics, University of the Punjab, Lahore 45590, Pakistan Institute of High Energy Physics, Chinese Acedemy of Sciences, Beijing 100049, China
(Received 2 December 2013; accepted 1 June 2014; published online 11 June 2014) We present simulation and test of an indirectly heated strip source electron beam gun assembly using Stanford Linear Accelerator Center (SLAC) electron beam trajectory program. The beam is now sharply focused with 3.04 mm diameter in the post anode region at 15.9 mm. The measured emission current and emission density were 1.12 A and 1.15 A/cm2 , respectively, that corresponds to power density of 11.5 kW/cm2 , at 10 kV acceleration potential. The simulated results were compared with then and now experiments and found in agreement. The gun is without any biasing, electrostatic and magnetic fields; hence simple and inexpensive. Moreover, it is now more powerful and is useful for accelerators technology due to high emission and low emittance parameters. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4883175] Indirectly heated strip cathode produces high beam currents and heating efficiency. Moreover, the practical heating temperature can be maximized and the thermal run away could be avoided.1 These guns are highly useful for melting and evaporation of refractory metals and for accelerators technology,2 due to high thermal load and long duty cycles. This is because of large surface area of the strip which serves as the source of electrons continuously. Some recent developments on this particular geometry have been reported in the literature.3–5 In continuation to our developments6–11 on electron guns, we have simulated the strip source electron gun for maximum practical emission current density and beam convergence in the post-anode region by computing charged particle trajectories using Stanford Linear Accelerator Center (SLAC) EGUN software.12 This is possible only if we focus the beam in a small area to the order of few millimeters. A detailed design and test of the assembly has been reported earlier in the same journal;10 hence, used the same spatial and voltage parameters for the simulation. A detailed diagram of the assembly is given in Figure 1. The geometrical parameters fixed for beam optimization are listed in Table I. Finally, simulations were compared with the experiments for then and now results. Potentials applied to different electrodes are given in Table II. Therefore, the obtained electron beam trajectories for the actual configuration are shown in Figure 2. The beam was not converged to a single point due to scattering in the post anode region. This measurement is compatible with Ref. 10, where we could not obtained any beam at the target, though 600 mA beam current was recorded at the output. Whereas, the trajectories for the optimized configuration given in Figure 3 exhibited that beam was focused in the post anode region at 15.9 mm where its diameter was measured to be 3.04 mm.
Emission current densities as a function of beam radius for the both configurations are shown in Figure 4. These profiles are plot normalized to 1.0 (with the peaks, as shown at the top of both plots); with values of maximum emission current density equal to 0.31 A/cm2 for the actual and 9.28 A/cm2 for the optimized configuration. The average values for these emission current densities were 0.063 A/cm2 and 1.15 A/cm2 , respectively. We also calculated average values of power densities for both configurations and obtained 0.63 kW/cm2 and 11.5 kW/cm2 for actual and optimized configurations, respectively. Figure 5 shows the phase space plot of two configurations, from which the emittance can be understood. A good convergent beam, with low emittance and no aberrations would have all the points lying in a straight line.12 We found total emittance 460.5 and 208.8 π mm mrad for the actual and the optimized configurations, whereas the normalized values were 91.56 and 41.5 π mm mrad, respectively.
a) Author to whom correspondence should be addressed. Electronic mail:
FIG. 1. Reprinted with permission from Rev. Sci. Instrum. 74, 1196, (2003). Copyright 2003 American Institute of Physics.
[email protected].
0034-6748/2014/85(6)/066106/3/$30.00
85, 066106-1
© 2014 AIP Publishing LLC
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 132.206.7.165 On: Thu, 11 Dec 2014 17:16:04
066106-2
Iqbal et al.
Rev. Sci. Instrum. 85, 066106 (2014)
TABLE I. Parameters fixed for beam optimization.
Parameters
Actual gun configuration (mm)
Optimized gun configuration (mm)
... 6.0 ... ... 15
6.1 8.5 2.4 13.35 13.4
Cathode to focusing electrode distance Cathode to anode distance Focusing electrode to anode distance Focusing electrode slit spacing Anode hole diameter
TABLE II. Potential applied to electrodes for the two configurations. Electrodes Cathode (kV) Focusing electrodes (kV) Anode (kV)
Actual gun
Optimized gun
−10 ... −4
−10 −10 0
FIG. 4. Current densities as a function of beam radius.
FIG. 2. Beam trajectories of the actual gun. FIG. 5. Phase space profiles of the both configurations
TABLE III. Emission parameters of the both configurations.
Parameters
Actual configuration
Optimized configuration
Beam diameter (mm) Beam focusing distance from anode (mm) Beam current (mA) Maximum current density (A/cm2 ) Average current density (A/cm2 ) Power density (kW/cm2 ) Total emittance (π mm mrad) Normalized emittance (π mm mrad)
Not focused Not focused 600 0.31 0.063 0.63 460.5 91.56
3.04 15.9 1120 9.28 1.15 11.5 208.8 41.5
FIG. 3. Beam trajectories of the optimized gun.
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066106-3
Iqbal et al.
Rev. Sci. Instrum. 85, 066106 (2014) TABLE IV. Measured results of the optimized design. Parameters Beam cross section (mm2 ) Beam current (mA) Current density (A/cm2 ) Power density (kW/cm2 ) Target distance from anode (mm)
FIG. 6. Measured beam profile at the SS target.
Values 3.15 × 35 1120 1.02 10.2 15.9
ble size of the length of the source. The beam current has been increased to more than 90%. The gun is now more powerful for refractory metals evaporations and has enhanced features for the use of accelerator technology due to high emission and low emittance of the beam. 1 J.
A summary of comparison of emission characteristics of both configurations of the gun is shown in Table III. Finally, the gun was tested experimentally by placing a SS target at the optimized distance (15.9 mm) in the post anode region. Figure 6 shows the beam profile obtained with 1120 mA beam current; has 3.15 × 35 mm2 cross section of the beam at the target. The measured current density for this profile was 1.02 A/cm2 that corresponds to power density 10.2 kW/cm2 , hence, confirmed the compatibility between the simulated and experimental results. After optimization of the gun, the experimentally measured results mentioned above are summarized in Table IV below. Thus, with the help of simulation by EGUN, we were able to determine the emission characteristics of the gun. The gun has been focused sharply at the target with the compara-
Yeheskel, D. Gazit, R. Avida, and M. Friedman, J. Phys. D 16, 499 (1983). 2 Z. Zhou and L. Bo, Chin Phys. C 29, 1196 (2005). 3 N. Maiti, K. Lijeesh, U. D. Barve, N. Quadri, G. U. Tembhare, S. Mukherjee, K. B. Thakur, and A. K. Das, Rev. Sci. Instrum. 84, 083302 (2013). 4 N. Maiti, S. Mukherjee, B. Kumar, U. D. Barve, V. B. Suryawanshi, and A. K. Das, Rev. Sci. Instrum. 81, 013302 (2010). 5 S. Mukherjee, N. Maiti, U. D. Barve, and A. K. Das, Vacuum 84, 920 (2010). 6 M. Iqbal, G. U. Islam, S. Saleem, and W. B. Herrmannsfeldt, Vacuum 101, 157 (2014). 7 M. Iqbal, G. U. Islam, Z. Zhou, and Y. Chi, Rev. Sci. Instrum. 84, 116107 (2013). 8 M. Iqbal, A. Wasy, and M. A. K. Lodhi, Rev. Sci. Instrum. 84, 056113 (2013). 9 M. Iqbal and F. Aleem, Rev. Sci. Instrum. 77, 106101 (2006). 10 M. Iqbal, M. A. Chaudhary, M. Rafiq, K. Masud, and F. Aleem, Rev. Sci. Instrum. 74, 1196 (2003). 11 M. Iqbal, K. Masud, M. Rafiq, M. A. Chaudhary, and F. Aleem, Rev. Sci. Instrum. 74, 4616 (2003). 12 W. B. Herrmannsfeldt, SLAC-331-UC-28, 1 (1988).
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitationnew.aip.org/termsconditions. Downloaded to IP: 132.206.7.165 On: Thu, 11 Dec 2014 17:16:04
