34results about How to "Improve short-term stability" patented technology

Methods and devices for calibrating a radiotherapy system are disclosed. The method includes providing a detection medium that responds to exposure to ionizing radiation, and preparing a calibration dose response pattern by exposing predefined regions of the detection medium to different ionizing radiation dose levels. The method also includes measuring responses of the detection medium in the predefined regions to generate a calibration that relates subsequent responses to ionizing radiation dose. Different dose levels are obtained by differentially shielding portions of the detection medium from the ionizing radiation using, for example, a multi-leaf collimator, a secondary collimator, or an attenuation block. Different dose levels can also be obtained by moving the detection medium between exposures. The disclosed device includes a software routine fixed on a computer-readable medium that is configured to generate a calibration that relates a response of a detection medium to ionizing radiation dose.

A dental implant can include a shaft defining a longitudinal axis and having an apical end, a coronal end, and an exterior surface. A portion of the exterior surface can include a porous material. The dental implant can include at least one thread, including a non-porous material, having an interior surface and a bone-engaging surface. The interior surface can engage and wind around the exterior surface of the shaft and the bone-engaging surface can extend outwardly from the exterior surface of the shaft. The shaft can include one or more channels configured to communicate a flowable material, stored within the shaft, to the exterior surface. Each channel can include an opening at the exterior surface to release the flowable material. At least one channel can extend between a cavity of the shaft and the exterior surface and can optionally be angled toward the apical end.

Position information of a movable body within an XY plane is measured with high accuracy by an encoder system whose measurement values have favorable short-term stability, without being affected by air fluctuations, and also position information of the movable body in a Z-axis direction orthogonal to the XY plane is measured with high accuracy by a surface position measuring system, without being affected by air fluctuations. In this case, since both of the encoder system and the surface position measuring system directly measure the upper surface of the movable body, simple and direct position control of the movable body can be performed.

A partial section of an aerial image measuring unit is arranged at a wafer stage and part of the remaining section is arranged at a measurement stage, and the aerial image measuring unit measures an aerial image of a mark formed by a projection optical system. Therefore, for example, when the aerial image measuring unit measures a best focus position of the projection optical system, the measurement can be performed using the position of the wafer stage, at which a partial section of the aerial image measuring unit is arranged, in a direction parallel to an optical axis of the projection optical system as a datum for the best focus position. Accordingly, when exposing an object with illumination light, the position of the wafer stage in the direction parallel to the optical axis is adjusted with high accuracy based on the measurement result of the best focus position.

A cold atom all-optical state selection device comprises vacuum flange, an optical state-selecting region, a magneto-optical trap, and a cavity base connected in sequence from top to bottom; when thecold atomic fountain clock starts to work, based on the magneto-optical trap cooling, trapping to get cold atomic groups and simultaneously preparing the clock state during the throwing of the cold atomic groups. The invention not only greatly increases the number density of the clock state atoms, but also shortens the height of the whole clock, thereby greatly shortening the dead time of the intermittent clock, thereby achieving the purpose of shortening the cycle and improving the short-term stability of the cold atomic clock. The device has a simple structure and is easy to implement, and can be used as a core device of a laser cold atomic clock.

The invention discloses a method and device for optimizing short-term stability parameters of an atomic frequency standard, belonging to the field of atomic frequency standards. Method: set multiple working parameter points; each working parameter point includes multiple experimental points and each experimental point corresponds to a different parameter to be optimized, and each parameter to be optimized corresponds to multiple experimental points and the number of corresponding experimental points is the same. The experimental points corresponding to the same parameter to be optimized are evenly distributed in the value range of the parameter to be optimized and include the two ends of the value range. There is at most one experimental point in every two working parameter points that is the same, and each experimental point is in all The number of occurrences in the working parameter points is equal; the parameters to be optimized include modulation depth, modulation frequency and microwave power; adjust the modulation depth, modulation frequency and microwave power according to each working parameter point; calculate the frequency discrimination of the atomic frequency standard corresponding to each working parameter point Slope, select the best working parameter point. The invention improves the short-term stability of the atomic frequency standard.

The invention discloses a moon observation system which is composed of an astronomical telescope, a ground-based microwave radiometer, a two-dimensional scanning mechanism and a controller. The systemis simple in structure and easy to implement. The ground-based microwave radiometer is installed on a two-dimensional turntable, the pitch angle of the initial position of the moon is obtained by theastronomical telescope, the initial position is calibrated by the controller, and the two-dimensional turntable is controlled to automatically track and scan the track of the moon; the moon brightness temperature signal is reflected by the antenna to enter an antenna feed system and enters a radiation receiver after polarization separation, and a voltage acquisition signal and a variance curve can be obtained in real time after detection and the moon brightness temperature value can also be calculated and thus the test efficiency can be effectively improved. The moon observation system has certain universality and can be applied to moon brightness temperature measurement based on ground-based microwave radiometers of different frequency bands to explore the stability and time distributioncharacteristics of microwave radiation characteristics.

The invention discloses high-stability combined region time service frequency generation equipment and aims to provide time service frequency generation equipment with high reliability, high length stability and a wide application range. The invention adopts the technical scheme that a receiving switching unit inputs two paths of selected satellite second signals from different sources into a locking unit to carry out frequency locking, two paths of phase-locked standard frequency signals generated by the locking unit and are respectively output to a signal processing unit A and a signal processing unit B; one path of satellite second signal is also used for carrying out frequency correction on a rubidium clock connected in parallel between a three-selection two-open device and a first analog phase-locked loop PLL_A, and one path of standard frequency signal is generated and transmitted to a signal processing unit C; and the signal processing units carry out signal shaping, amplification, shunting and coding on three paths of standard frequency signals from different sources, the obtained signals are subjected to frequency division, output to a far-end time service unit and are converted into optical signals by an optical-electrical converter, and the optical signals are transmitted to an equipment machine room by one or multiple paths of optical fibers and then are converted into electric signals, and the electric signals are transmitted by an antenna so as to complete a clock time service of a receiving end.

The invention discloses a broadband and wide-range locking method and system of the repetition frequency of an optical frequency comb. The invention adopts the switch phase detection scheme to increase the dynamic range of error signal identification, so that the repetition frequency locking system of the optical frequency comb is not easy to lose lock. . Use the fast PI controller to control the EOM in the optical system to achieve high-speed control in the range of tens of Hz and MHz bandwidth, and improve the short-term stability of repetition frequency locking; use the slow PI controller to control the PZT in the optical system to achieve a range of several kHz and tens of kHz The medium-speed control of the bandwidth improves the mid- and long-term stability of the repetition frequency locking; the ultra-slow PI controller is used to control the temperature of the optical system cavity to achieve low-speed control in the range of tens of kHz and less than 1Hz bandwidth, and improve the long-term stability of the repetition frequency locking Spend.

The invention discloses a coherent population trapping an atomic frequency standard and a method for improving its short-term stability, belonging to the field of atomic frequency standards. The atomic frequency standard includes: a voltage-controlled crystal oscillator; a linear polarization excitation unit, which is used to generate a microwave search signal according to the output frequency of the voltage-controlled crystal oscillator; a physical unit, which is used to generate an optical detection signal under the action of the microwave search signal; a servo loop, It is used to perform synchronous phase detection on the optical detection signal to generate a synchronous phase detection signal; the control unit is used to generate a correction voltage based on the synchronous phase detection signal to act on the voltage-controlled crystal oscillator; the system relaxation time detection unit is used to detect the atomic frequency standard system Relaxation time Δt; the control unit is also used for timing control of the optical switch and servo loop in the physical unit according to the system relaxation time Δt, after controlling the optical switch in the physical unit to be turned on for N Δt time lengths, control The servo loop performs synchronous phase detection on the optical detection signal generated by the physical unit.

A device for actively calibrating the phase of a microwave signal transmitted by an optical fiber using a photoelectric oscillator includes: a central station and a base station, and the central station and the base station are connected through a single-mode optical fiber. The invention can overcome the disadvantages of traditional electronic methods in terms of bandwidth, weight, volume, electromagnetic interference, etc., and break through the bottleneck of electronic technology to realize stable phase transmission of high-frequency microwave signals.

The invention discloses a laser frequency stabilization system, belonging to the field of lasers. The system includes: a reference laser, a first electro-optic modulator, a first polarization beam splitter, a first half-wave plate, a Fabry-Perot interferometer, a second half-wave plate, a second polarization beam splitter, a second electro-optic Modulator and laser to be stabilized; Piezoelectric ceramics, the first driving source that outputs the first reference signal to the first electro-optic modulator, the first photoelectric unit that is arranged on the reflected optical path of the first polarization beam splitter prism, and the first oscillation signal A first mixer for mixing with the frequency signal output by the first photoelectric unit, a driving source for generating a voltage signal according to the signal output by the first mixer; a second driving source for outputting a second reference signal to the second electro-optical modulator The source is a second photoelectric unit arranged on the reflected optical path of the second polarization beam splitter, and a second mixer for mixing the second oscillation signal and the frequency signal output by the second photoelectric unit.