A dual-energy pyroelectric accelerator

Abstract

Pyroelectric crystals have been known as portable particle accelerators for more than a decade. With a single 10 mm thick × 30 mm diameter LiTaO3 z-cut pyroelectric crystal, we have produced a dual-energy electron beam with energies of 120 keV up to 190 keV without need to any enhancement of electric field. The dual-energy beam is achieved using a low-density polyethylene chamber surrounding the crystal. The chamber is designed and fabricated to trap the emitted electrons from the crystal's surface. The created electric field by the trapped electrons produce an electron beam with a different energy. Moreover, using the chamber around the crystal mitigate the electrical breakdown on its surface and, therefore, the accelerator's potential is increased.

Calculating the maximum possible yield for a typical pyroelectric neutron generator

“…These faces are named 𝑍 + and 𝑍 − (see figure 1). If the crystal experiences a temperature increase, a negative and positive electric charge will be created on the 𝑍 + and 𝑍 − faces, respectively [6]. The magnitude of the electric charge, 𝑄, is given by…”

“…Thus, a large electric field is created around the crystal. The produced electric field due to a temperature change of tens of degrees is large enough to accelerate electrons/ions to energies of hundreds of keV [6]. By locally enhancing the created electric field, the D 2 gas around the crystal is ionized and is accelerated into a deuterated/tritiated target.…”

Registration of a pulsed generation of electron beam in the nanosecond range under heating and cooling cycles of a lithium niobate crystal at atmospheric pressure

“…Pyroelectric LiNbO 3 and LiTaO 3 crystals are successfully used for generation of accelerated fluxes of charged particles, X-ray radiation, and neutrons [1][2][3][4][5][6][7][8][9]. These processes are usually initiated due to changes in the bound charge density that develops on the surfaces of polar Z-cut lithium niobate and tantalate crystals in the heating/cooling cycles due to the pyroelectric effect.…”

“…To this end, firstly, the ratios of the diameters of the screw head (8) and the copper insert (9) to the corresponding inner diameter of the anode (𝑑 𝐴 = 14 mm) were selected to be approximately 2.3 (see, for example,[14]). Secondly, a MELF-type matching cylindrical resistor (5) with a diameter of 2.2 mm was placed between the screw head (8) and copper insert(9), and was centered using bead (10) made of turbonit with a relative permittivity 𝜀 𝑟 ≈ 5.The cathode block (C) was electrically grounded and placed on an electrically controlled heater which allowed varying the temperature of lithium niobate crystal (1) from 20 • C to 80 • C at a rate of no more than 9 • C/min. The temperature of the cathode block was monitored by a K-type thermocouple (chromel-aluminum) contacted with its outer cylindrical surface.…”

Indicators of upcoming electric breakdown in a pyroelectric accelerator

“…As is well known, temperature change (pyroelectric effect), 3) mechanical compression/expansion (piezoelectric effect), 4) as well as friction (triboelectric effect) 5) can initiate the generation of high electric field potential due to polarization of certain dielectric materials. It has been repeatedly demonstrated that pyroelectric materials (usually single crystals of lithium niobate or tantalate) driven by a temperature change can be used to generate and accelerate electrons [6][7][8][9][10][11][12][13] and ions. [14][15][16] The concept of the pyroelectric accelerator has been introduced by several groups.…”