عنوان المقالة:Back bombardment for dispenser and lanthanum hexaboride cathodes
محمود عبد العظيم بكر | Mahmoud Abdel Aziem Bakr | 4949
- نوع النشر
- مجلة علمية
- المؤلفون بالعربي
- Physical Review Special Topics-Accelerators and Beams
- الملخص العربي
- The back bombardment (BB) effect limits wide usage of thermionic rf guns. The BB effect induces not only ramping-up of a cathode’s temperature and beam current, but also degradation of cavity voltage and beam energy during a macropulse. This paper presents a comparison of the BB effect for the case of dispenser tungsten-base (DC) and lanthanum hexaboride (LaB6) thermionic rf gun cathodes. For each, particle simulation codes are used to simulate the BB effect and electron beam dynamics in a thermionic rf gun cathode. A semiempirical equation is also used to investigate the stopping range and deposited heat power of BB electrons in the cathode material. A numerical simulation method is used to calculate the change of the cathode temperature and current density during a single macropulse. This is done by solving two differential equations for the rf gun cavity equivalent circuit and one-dimensional thermal diffusion equation. High electron emission and small beam size are required for generation of a high-brightness electron beam, and so in this work the emission properties of the cathode are taken into account. Simulations of the BB effect show that, for a pulse of 6 μs duration, the DC cathode experiences a large change in the temperature compared with LaB6, and a change in current density 6 times higher. Validation of the simulation results is performed using experimental data for beam current beyond the gun exit. The experimental data is well reproduced using the simulation method.
- تاريخ النشر
- 22/06/2011
- الناشر
- American Physical Society
- رابط DOI
- 10.1103/Ph
- الكلمات المفتاحية
- BackBombardment, FEL