Laser Processed Oxygen-Free High-Conductivity Copper with Ti and Ti–Zr–V–Hf Films Applied in Neutron Tube

Abstract

The laser processing method has proven to produce surfaces while ensuring a low secondary electron yield of oxygen-free high-conductivity copper (OFHC) samples, making it attractive for electron cloud mitigation in next-generation particle accelerators and neutron tubes. In this work, the laser processing method is proposed to OFHC targets for the first time, aiming to reduce the secondary electrons in the neutron tube. The secondary electron yields (SEYs) and the thermal conductivities of Ti film and quaternary Ti–Zr–V–Hf films with unprocessed and laser processed OFHC substrates are investigated. Our results highlight that the thermal conductivity of Ti film with laser processed OFHC substrates is in proximity to the cleaned bare OFHC sample, especially at high temperatures. Moreover, the SEY of coated OFHC substrates are higher than that of coated laser processed substrates, which indicates the better secondary electron suppression capability of coated laser processed substrates. Therefore, the thermal conductivity and SEY results illustrate that the application of Ti and Ti–Zr–V–Hf coated laser processed OFHC can be considered to improve the neutron yield in neutron tubes in the future.

Structural and Secondary Electron Yield Properties of Titanium–Palladium Films with Laser-Treated Copper Substrate for Application in Neutron Generators

“…Compared with Ti and Ti–Pd films with untreated OFHC substrates, the surface roughness and surface area of Ti and Ti–Pd films with laser-treated OFHC substrates were obviously increased. As reported in the previous studies, the thermal conductivity of Ti film with laser-treated OFHC substrates was 3.5–11.5% higher than the one with untreated OFHC substrates measured from 25 to 300 °C [ 26 ]. It can be speculated that the thermal conductivity of Ti and Ti–Pd films with laser-treated OFHC substrates is also higher than those with untreated OFHC substrates.…”

“…This indicated that the surface of sample #2 was basically covered by Ti film, while the surface of sample #4 was basically covered by Pd film. It can be speculated that C, N, and O elements were mostly introduced during sample transferal in the air [ 26 ]. As shown in Figure 6 b, it can be seen that the O 1s peak and Pd 3p 3/2 peak overlapped.…”

“…The secondary electrons emitted inside the porous structure are more likely to be trapped during collisions with the porous surface walls, resulting in a decrease in SEY. Specific to the application of the neutron generator, the porous target surface produced by laser ablation can also effectively suppress secondary electron emission without the introduction of any additional components [ 26 ]. Many works have been focusing on the principle and simulation of laser ablation to reduce SEY [ 27 ], and the accelerator tests on the laser-engineering surface are carried out [ 28 ].…”

“…For the first time, the influence of laser parameters on SEY was explored [ 24 ]. In addition, TiZrVHf film coating on laser-treated aluminum alloy and OFHC substrates was also studied [ 26 , 29 ].…”

Activation of Zr, ZrVHf and TiZrV Non-Evaporative Getters Characterized by In Situ Synchrotron Radiation Photoemission Spectroscopy

“…Non-evaporable getters (NEG) technology was first invented at CERN in the 1990s [1] and are now widely employed in particle accelerators [2] the Tokamak fusion test reactor [3], field-emission display, vacuum packaged MEMS [4] and neutron tubes [5].NEG materials have become an integral component of many ultrahigh vacuum environments mainly due to their unique surface properties, which are conducive to achieving ultrahigh vacuum (UHV) of the order of at least 10 −8 Pa [6,7] by chemically adsorbing gas molecules on their surface. Heat needs to be applied to the NEG to allow the surface gas to residually diffuse into the bulk before it can have pumping performance; this process is called "activation".…”