| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Tuesday Sessions |
| Session TF-TuP |
| Session: | Thin Films Poster Session |
| Presenter: | Masahito Tagawa, Kobe University, Japan |
| Authors: | M. Tagawa, Kobe University, Japan K. Yokota, Kobe University, Japan T. Yasukochi, Kobe University, Japan S.K. Chee, Mechano Transformer Corporation, Japan |
| Correspondent: | Click to Email |
A pulsed supersonic valve (PSV) with fast operation capability is essential for many molecular/atomic beam experiments. A reliable PSV is a key device for not only scientific molecular beam experiments, but also engineering applications such as future digital molecular beam epitaxy (MBE) and molecular beam-induced etching. Among these applications, laser-detonation hyperthermal beam source, which has been applied for space environmental effect studies on thin film erosion, requires highly reliable and fast response PSV system. We have developed a fast and reliable piezoelectric-driven PSV system. It consists of conventional low-voltage piezoelectric actuator (max 150V) with a displacement enlargement mechanism (displacement is greater than 0.1mm) . These mechanisms are covered by a stainless steel body. Size of PSV is approximately 15 x 10 x 4 cm. Gas is ejected by a 1 mm hole. The poppet clearance is adjustable by the micrometer. The poppet system with a Viton O-ring and Au reflector was specially designed for laser-detonation applications, which requires the focusing 7 J laser pulse near the O-ring. A pressure profile of ejected gas from the nozzle was measured. It is clearly indicated that the PSV is able to operate less than 100 microseconds. It should be mentioned that even faster operation is possible with a high-current PSV driver. It was also confirmed the specification below;
Max. Pressure of supply gas: > 0.8 MPa, Max. Repetition rate: > 50 Hz, Poppet life: > 0.6 million shot (with CO2 laser irradiation)
One of the unique features of this system is that two PSVs independently eject gas pulses into one hole, such that time-variation of the composition of a gas pulse could be controlled. This capability provides controllability of the dissociation of molecules in a pulsed laser plasma.
Time-of-flight spectra of “thermal” molecular beam generated with this PSV system were measured. It was obvious that the velocity distribution was consistent with the Maxwell-Boltzmann distribution. Also the capability of forming “hyperthermal” atomic beam with laser-detonation for space environmental simulation of thin film erosion problems as well as a wide variety of applications on applied surface sciences of this fast and reliable PSV system will also be discussed.
A part of this research was supported by the Grant-in-Aids for Scientific Research from JSPS under contract Nr. 25289307, 26289322, 15K14252 and 15K14253. Financial support through the Coordination Funds for Promoting Aerospace Utilization from the MEXT was also appreciated.