ABSTRACT
We report on the first subpicometer interferometer flown in space. It was part of ESA's Laser Interferometer Space Antenna (LISA) Pathfinder mission and performed the fundamental measurement of the positional and angular motion of two free-falling test masses. The interferometer worked immediately, stably, and reliably from switch on until the end of the mission with exceptionally low residual noise of 32.0_{-1.7}^{+2.4} fm/sqrt[Hz], significantly better than required. We present an upper limit for the sensor performance at millihertz frequencies and a model for the measured sensitivity above 200 mHz.
ABSTRACT
Future drag-free missions for space-based experiments in gravitational physics require a Gravitational Reference Sensor with extremely demanding sensing and disturbance reduction requirements. A configuration with two cubical sensors is the current baseline for the Laser Interferometer Space Antenna (LISA) and has reached a high level of maturity. Nevertheless, several promising concepts have been proposed with potential applications beyond LISA and are currently investigated at HEPL, Stanford, and EADS Astrium, Germany. The general motivation is to exploit the possibility of achieving improved disturbance reduction, and ultimately understand how low acceleration noise can be pushed with a realistic design for future mission. In this paper, we discuss disturbance reduction requirements for LISA and beyond, describe four different payload concepts, compare expected strain sensitivities in the "low-frequency" region of the frequency spectrum, dominated by acceleration noise, and ultimately discuss advantages and disadvantages of each of those concepts in achieving disturbance reduction for space-based detectors beyond LISA.
ABSTRACT
To maintain mobility in patients with chronic hypoxemia who are under long-term oxygen therapy, portable oxygen systems are available. They have the disadvantage of a short range. To prolong the range and to reduce the cost of oxygen treatment, demand oxygen delivery systems (DODS) are used. Aim of the study was to compare three DODS (DOC-2000 [D], TransTracheal Inc.; Oxytron [O], Weinmann; Pulsair [P], DeVilbiss, Sunrise Medical) with continuous oxygen delivery. 17 patients (age 67.82 +/- 9.46 years; FEV1 1.23 +/- 0.69 l; PaO2 48.8 +/- 6.7 mm Hg) were studied. The continuous flow oxygen (CONT) and the DODS were applied to the patients for 30 minutes each in random sequence with an airflow of 2 l/min. After 15 and 30 minutes arterial blood gas analysis was done. Oxygen saturation was recorded continuously by pulseoximetry. After 15 minutes no significant differences in PaO2 were found between CONT and DODS. After 30 minutes no significant difference in PaO2 was found in CONT as compared to P. Significant lower PaO2 values were found for O and D as compared to CONT (p < 0.01). With P the range of a portable oxygen source was increased by 161.5 percent, with O by 172 percent, with D the range was increased by only 17.2 percent. Prolongation of range of a portable oxygen source can be achieved by means of DODS without a decrease of PaO2 and thus without loss of quality of the oxygen treatment. However, there are differences in efficacy between the DODS.
Subject(s)
Lung Diseases, Obstructive/therapy , Oxygen Inhalation Therapy/instrumentation , Oxygen Inhalation Therapy/methods , Adult , Aged , Aged, 80 and over , Female , Forced Expiratory Volume , Humans , Lung Diseases, Obstructive/physiopathology , Male , Middle Aged , Oxygen/blood , Partial Pressure , Time FactorsABSTRACT
A subpicosecond KrF* laser system capable of producing 20 +/- 2-mJ pulses has been developed. The means of producing ultrashort seed pulses for the KrF* amplifier system and characteristics of the full system are described. It is shown that efficient subpicosecond energy extraction is possible.
