Volume 78, Issue 10, October 2007
Index of content:
- PARTICLE SOURCES, OPTICS AND ACCELERATION; PARTICLE DETECTORS
A ground-based radio frequency inductively coupled plasma apparatus for atomic oxygen simulation in low Earth orbit78(2007); http://dx.doi.org/10.1063/1.2800766View Description Hide Description
A radio frequency (rf) inductively coupled plasma apparatus has been developed to simulate the atomic oxygen environment encountered in low Earth orbit (LEO). Basing on the novel design, the apparatus can achieve stable, long lasting operation, pure and high density oxygen plasma beam. Furthermore, the effective atomic oxygen flux can be regulated. The equivalent effective atomic oxygen flux may reach at an oxygen pressure of and rf power of . The equivalent atomic oxygen flux is about 100 times than that in the LEO environment. The mass loss measured from the polyimide sample changes linearly with the exposure time, while the density of the eroded holes becomes smaller. The erosion mechanism of the polymeric materials by atomic oxygen is complex and involves initial reactions at the gas-surface interface as well as steady-state material removal.
78(2007); http://dx.doi.org/10.1063/1.2800751View Description Hide Description
A compact high power pulsed modulator based on spiral water Blumlein line, which consists of primary storage capacitors, a Tesla transformer, a spiral Blumlein line of water dielectric, and a field-emission diode, is described. The experimental results showed that the diode voltage is more than , the electron beamcurrent of diode is about , and the pulse duration is about . The distributions for electrical field in the spiral water Blumlein line were obtained by the simulations. In addition, the process of the charging a spiral Blumlein line was simulated through the PSPICE software to get the wave form of charging voltage of pulse forming line, the diode voltage, and diode current of modulator. The theoretical and simulated results are in agreement. This accelerator is very compact and works stably and reliably.
78(2007); http://dx.doi.org/10.1063/1.2804074View Description Hide Description
An analytical expression relating mass and position of a particle attached on a cantilever to the resulting change in cantilever resonant frequency is derived. Theoretically, the position and mass of the attached particle can be deduced by combining measuredresonant frequencies of several bending modes. This finding is verified experimentally using a microscale cantilever with and without an attached gold bead. The resonant frequencies of several bending modes are measured as a function of the bead position. The bead mass and position calculated from the measuredresonant frequencies are in good agreement with the expected mass and the position measured.