Laser Alignment System Research Articles

Optimization of crystal phase-matching angle metrology instrument and error analysis

Finding the optimal phase matching angle of a potassium dihydrogen phosphate (KDP) crystal is vital for increasing the harmonic conversion efficiency, which plays a key role in Inertial Confinement Fusion (ICF). The aim of this study was to build and optimize an instrument, which can measure the optimal phase matching angle of a KDP crystal accurately. We designed and tested a new beam path, which made the alignment process much simple. We studied the temperature compensation method and applied it in the instrument. Several methods were used to investigate and reduce the errors of the instrument. The errors from laser energy, transmission unit, alignment system, energy meter, temperature, and environmental vibration were analyzed and optimized. The measurement accuracy of the instrument is 10 μradians in phase matching angle. The instrument had been manufactured and applied well in the laser fusion facility, which can save a lot of time and money.

Misalignment effect on gearbox failure: An experimental study

Overhang-meshing gears, deflection of pinion/gear shaft, bearing wear, assembly error, poor adjustment of bearings and foundation are the reasons of misalignment in gear drives.In the present work, the misalignment effect on gearbox failure is investigated experimentally using vibration analysis. Misalignment between motor and gearbox is measured using laser alignment system (LAS). The effect of input shaft speed and load on the gearbox failure is also discussed.The misalignment effect primarily observes on the gearbox drive end taper roller bearing and distresses gear transmission. Physical and microscopic examinations of the dismantle gearbox confirm similar findings as observe from vibration spectrum. Severe damages in taper roller bearing (32206) and multiple pits on all the rollers and cone. The bearing cage is deformed badly due to overload and misalignment. The effect of bearing failure on gear’s damage is also investigated. Non-uniform contact patch is observed on the meshing gears in the plane of action. Misalignment results in scuffing failure on the pinion addendum and gear dedendum regions due to limited lubricant in the overstress region. At the end of the test, all the four seals appears safe, while the coupling spiders damage seriously.

Online condition monitoring of misaligned meshing gears using wear debris and oil quality sensors

PurposeThis paper aims to investigate the effect of misalignment on wear of spur gears and on oil degradation using online sensors.Design/methodology/approachThe misalignment effect on gears is created through a self-alignment bearing, and is measured using laser alignment system. Several online sensors such as Fe-concentration sensor, moisture sensor, oil condition sensor, oil temperature sensor and metallic particle sensor are installed in the gear test rig to monitor lubricant quality and wear debris in real time to assess gearbox failure.FindingsOffset and angular misalignments are detected in both vertical and horizontal planes. The failure of misaligned gear is observed at both the ends and on both the surfaces of the gear teeth. Larger-size ferrous and non-ferrous particles are traced by metallic particle sensor due to gear and seal wear caused by misalignment. Scanning electron microscope (SEM) images examine chuck, spherical and flat platelet particles, and confirm the presence of fatigue (pitting) and adhesion (scuffing) wear mechanism. Energy-dispersive X-ray spectroscopy analysis of SEM particles traces carbon (C) and iron (Fe) elements due to gear failure.Originality/valueGear misalignment is one of the major causes of gearbox failure and the lubricant analysis is as important as wear debris analysis. A reliable online gearbox condition monitoring system is developed by integrating wear and oil analyses for misaligned spur gear pair in contact.

In-flight performance of the Canadian Astro-H Metrology System

The Canadian Astro-H Metrology System (CAMS) on the Hitomi X-ray satellite is a laser alignment system that measures the lateral displacement (X/Y) of the extensible optical bench (EOB) along the optical axis of the hard X-ray telescopes (HXTs). The CAMS consists of two identical units that together can be used to discern translation and rotation of the deployable element along the axis. This paper presents the results of in-flight usage of the CAMS during deployment of the EOB and during two observations (Crab and G21.5-0.9) with the HXTs. The CAMS was extremely important during the deployment operation by providing real-time positioning information of the EOB with micrometer scale resolution. In this work, we show how the CAMS improves data quality coming from the hard X-ray imagers. Moreover, we demonstrate that a metrology system is even more important as the angular resolution of the telescope increases. Such a metrology system will be an indispensable tool for future high resolution X-ray imaging missions.

Laser proton accelerator with improved repeatability at Peking University

The repeatability of laser proton accelerator is mainly limited by laser plasma interaction, laser target coupling and laser parameter variation. In our recent experiments performed on the Compact Laser Plasma Accelerator at Peking University, gain of proton beams with improved repeatability is demonstrated. In order to control the laser plasma interaction in pre-plasma, cross polarized-wave generation technique is employed to provide a laser pulse with an ultrahigh contrast of 10−10 A semi-automatic laser and target alignment system with a sensitivity of few microns is employed. The repetition rate of the laser pro-ton accelerator is at the level of 0.1 Hz which is beneficial to decrease laser parameter variation. The shot-to-shot variation of proton energies is about 9% for a level of confidence of 0.95.

Mechanical stability of the CMS strip tracker measured with a laser alignment system

The CMS tracker consists of 206 m2 of silicon strip sensors assembled on carbon fibre composite structures and is designed for operation in the temperature range from −25 to +25°C. The mechanical stability of tracker components during physics operation was monitored with a few μm resolution using a dedicated laser alignment system as well as particle tracks from cosmic rays and hadron-hadron collisions. During the LHC operational period of 2011–2013 at stable temperatures, the components of the tracker were observed to experience relative movements of less than 30μm. In addition, temperature variations were found to cause displacements of tracker structures of about 2μm°C, which largely revert to their initial positions when the temperature is restored to its original value.

TU-FG-BRB-12: Real-Time Visualization of Discrete Spot Scanning Proton Therapy Beam for Quality Assurance

Purpose: With the growing adoption of proton beam therapy there is an increasing need for effective and user-friendly tools for performing quality assurance (QA) measurements. The speed and versatility of spot-scanning proton beam (PB) therapy systems present unique challenges for traditional QA tools. To address these challenges a proof-of-concept system was developed to visualize, in real-time, the delivery of individual spots from a spot-scanning PB in order to perform QA measurements. Methods: The PB is directed toward a custom phantom with planar faces coated with a radioluminescent phosphor (Gd2O2s:Tb). As the proton beam passes through the phantom visible light is emitted from the coating and collected by a nearby CMOS camera. The images are processed to determine the locations at which the beam impinges on each face of the phantom. By so doing, the location of each beam can be determined relative to the phantom. The cameras are also used to capture images of the laser alignment system. The phantom contains x-ray fiducials so that it can be easily located with kV imagers. Using this data several quality assurance parameters can be evaluated. Results: The proof-of-concept system was able to visualize discrete PB spots with energies ranging from 70 MeV to 220 MeV. Images were obtained with integration times ranging from 20 to 0.019 milliseconds. If not limited by data transmission, this would correspond to a frame rate of 52,000 fps. Such frame rates enabled visualization of individual spots in real time. Spot locations were found to be highly correlated (R2=0.99) with the nozzle-mounted spot position monitor indicating excellent spot positioning accuracy Conclusion: The system was shown to be capable of imaging individual spots for all clinical beam energies. Future development will focus on extending the image processing software to provide automated results for a variety of QA tests.

Development of a high magnetic field assisted pulsed laser deposition system.

A high magnetic field assisted pulsed laser deposition (HMF-PLD) system has been developed to in situ grow thin films in a high magnetic field up to 10 T. In this system, a specially designed PLD cylindrical vacuum chamber is horizontally located in the bore configuration of a superconducting magnet with a bore diameter of 200 mm. To adjust the focused pulsed laser into the target in such a narrow PLD vacuum chamber, an ingeniously built-in laser leading-in chamber is employed, including a laser mirror with a reflection angle of 65° and a damage threshold up to 3.4 J/cm(2). A laser alignment system consisting of a built-in video-unit leading-in chamber and a low-energy alignment laser is applied to monitor and align the pulsed laser propagation in the PLD vacuum chamber. We have grown La0.7Sr0.3MnO3 (LSMO) thin films on (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) [LSAT (001)] substrates by HMF-PLD. The results show that the nanostructures of the LSMO films can be tuned from an epitaxially continuous film structure without field to a vertically aligned nanorod structure with an applied high magnetic field above 5 T, and the dimension size of the nanorods can be tuned by the strength of the magnetic field. The associated magnetic anisotropy is found to be highly dependent on the nanorod structures. We show how the HMF-PLD provides an effective route toward tuning the nanostructures and the physical properties of functional thin films, giving it an important role in development of nanodevices and their application.

Feasibility study of patient motion monitoring by using tactile array sensors

An ideal alignment method based on the external anatomical surface of the patient should consider the entire region of interest. However, optical-camera-based systems cannot blindly monitor such areas as the patient’s back, for example. Furthermore, collecting enough information to correct the associated deformation error is impossible. The study aim is to propose a new patient alignment method using tactile array sensors that can measure the distributed pressure profiles along the contact surface. The TactArray system includes one sensor, a signal-conditioning device (USB drive/interface electronics, power supply, and cables), and a PC. The tactile array sensor was placed between the patient’s back and the treatment couch, and the deformations at different location on the patient’s back were evaluated. Three healthy male volunteers were enrolled in this study, and pressure profile distributions (PPDs) were obtained with and without immobilization. After the initial pretreatment setup using the laser alignment system, the PPD of the patient’s back was acquired. The results were obtained at four different times and included a reference PPD dataset. The contact area and the center-of-pressure value were also acquired based on the PPD data for a more elaborate quantitative data analysis. To evaluate the clinical feasibility of using the proposed alignment method for reducing the deformation error, we implemented a real-time self-correction procedure. Despite the initial alignment, we confirmed that PPD variations existed in both cases of the volunteer studies (with and without the use of the immobilization tool). Additionally, we confirmed that the contact area and the center of pressure varied in both cases, and those variations were observed in all three volunteers. With the proposed alignment method and the real-time selfcorrection procedure, the deformation error was significantly reduced. The proposed alignment method can be used to account for the limitation of the camera-based system and to improve the accuracy of the external surface-based patient setup.

Performance of a NSRRC In-Vacuum Undulator

An advanced undulator technology is critical for highly brilliant synchrotron radiation in a third-generation light source. Taiwan Photon Source (TPS) is a light source of intermediate energy, and a short magnet period of an undulator is desired for experimental stations using hard X-rays. In-vacuum undulators have been delivered and tested at the NSRRC site before installation in the storage ring. The vacuum tests were performed first to ensure an ultra-high vacuum (below 2 ×10-10 torr). Magnetic measurement is comprised of laser alignment system that was developed at NSRRC. The results show satisfactory field repeatability after assembly of the vacuum chamber, because phase errors of both undulators are less than 3°. Baking an undulator was performed to achieve an ultra-high vacuum. Here, we describe the results from the acceptance tests.

CMS Silicon Strip alignment and monitoring with the Laser Alignment System

The alignment of the CMS Silicon Strip detector can be monitored using its built-in Laser Alignment System. The 32 Laser beams in endcaps and the eight Laser beams connecting the barrel and the endcap regions make it possible to monitor the alignment changes to a precision better than 10μm and the measurement of the absolute alignment parameters better than 100μm.For this, 434 of the Silicon Strip modules (3%) are illuminated by the Laser beams, assuring a continuous surveillance during the collisions and cosmics data taking. In this contribution the status and the preliminary results of monitoring and alignment parameters during the 2011 data taking period at the Large Hadron Collider (LHC) are presented.

The CMS Silicon Tracker Alignment

The alignment of the Strip and Pixel Tracker of the Compact Muon Solenoid experiment, with its large number of independent silicon sensors and its excellent spatial resolution, is a complex and challenging task. Besides high precision mounting, survey measurements and the Laser Alignment System, track-based alignment is needed to reach the envisaged precision. Three different algorithms for track-based alignment were successfully tested on a sample of cosmic-ray data collected at the Tracker Integration Facility, where 15% of the Tracker was tested. These results, together with those coming from the CMS global run, will provide the basis for the full-scale alignment of the Tracker, which will be carried out with the first p - p collisions.

진단용 CT-모의치료기 테이블의 효율적인 교정 방법

본 연구는 진단용 CT 장치를 이용한 CT-모의치료기의 테이블 및 레이저 정렬 시스템과 횡단면 영상의 중심간 정렬을 개선하기 위한 효율적인 방법을 제안하고자 하였다. 본원에서 제작한 팬텀을 이용하여 AAPM TG66에서 제시하는 일일 정도관리를 시행하고 기하학적 삼각함수를 이용하여 레이저 정렬 시스템을 교정하였으며 교정 전, 후를 비교함으로서 교정방법에 대한 효율성을 검토하였다. 교정 전 영상의 중심간 오차는 3.82mm, 테이블 종축은 <TEX>$0.436^{\circ}$</TEX> 틀어져 진행하였다. 기하학적 삼각함수를 이용한 레이저 정렬 시스템의 교정 후 0.7mm의 중심간 오차가 발생하여 <TEX>${\pm}2mm$</TEX>의 허용오차 범위를 만족하였다. 설치 가동 중인 진단용 CT 장치를 방사선치료 전용 CT-모의치료기로 활용하는 경우 기하학적 정확도를 만족시키기 위한 테이블 교정은 기술적인 한계 뿐 만 아니라 시간 및 경제적 손실에 비하여 매우 비효율적이다. 그러나 레이저 정렬 시스템을 이용한 교정 방법은 경제적이고 비교적 간단하면서도 만족스러운 기하학적 정확도를 얻을 수 있어 임상에서 적용할 수 있는 효율적인 방법이라 사료된다. This study suggested that the table of CT-simulator and the laser alignment system using diagnostic CT scanner have an efficient method for improvement in alignment between the planned target center of traverse image with CT scanner. It was conducted on the daily QA when presented in the AAPM TG66 with correcting the laser alignment system using geometric trigonometric functions and investigated the effectiveness of correction methods as compared with those before and after correction. Before correction error was 3.82mm between the planned target center of image, the table longitudinal axis was twisted with 0.436o. The laser alignment system using geometric trigonometric functions in after correction was satisfied with tolerance limits of <TEX>${\pm}2mm$</TEX> when occurred about 0.7mm in errors between the planned target center. The table correction to satisfy the geometric accuracy is very inefficient over against the time and economic loss as well as technical limits in the case of application as only radiation therapy associated with CT-simulator with diagnostic CT scanner in use. But, the method which corrects the laser alignment system is economic and relatively simple with possibility of getting well geometric accuracy and we suppose that it is efficient method for applying in the clinic.

Alignment of the CMS silicon strip tracker during stand-alone commissioning

The results of the CMS tracker alignment analysis are presented using the data from cosmic tracks, optical survey information, and the laser alignment system at the Tracker Integration Facility at CERN. During several months of operation in the spring and summer of 2007, about five million cosmic track events were collected with a partially active CMS Tracker. This allowed us to perform first alignment of the active silicon modules with the cosmic tracks using three different statistical approaches; validate the survey and laser alignment system performance; and test the stability of Tracker structures under various stresses and temperatures ranging from +15 °C to −15 °C. Comparison with simulation shows that the achieved alignment precision in the barrel part of the tracker leads to residual distributions similar to those obtained with a random misalignment of 50 (80) μm RMS in the outer (inner) part of the barrel.

An axis of rotation alignment system for high-resolution pinhole SPECT imaging

We developed a simple geometric calibration method for modified animal pinhole single photon emission computed tomography (SPECT) imaging systems using a laser alignment system that does not require additional calibration scans, and verified the feasibility of this system. An optical system consisting of a laser generator and a reflecting mirror, and an alignment method using this system were developed. After laser alignment had been completed, SPECT scans of a Tc-99m line source were performed. After acquiring data with complete alignment, the rotation stage was moved along the y-axis (parallel to the detector plane) to acquire off-axis data. Using these on- and off-axis settings, a micro-performance phantom with hot-rod inserts was scanned after filling with Tc-99m solution. Reconstructed images of the line source and the hot-rod phantom showed that image degradation was minimized when the rotation center was completely aligned using our system. The spatial resolution of the reconstructed image measured using the line source was finest under complete alignment. Under this condition, the smallest hot rod (1.2mm diameter) was resolved in the SPECT image acquired using a 0.5mm pinhole aperture. The effects of misalignment were clearly observable in off-axis images; only hot rods with more than 3.2mm diameter were resolved in 1mm off-axis image whereas there were no resolvable hot rods with more than 2mm off-axis image. This system of which the feasibility was verified in the present study will be useful for low-cost molecular imaging studies using single photon emitting tracers.

The laser alignment system for the CMS silicon microstrip tracker

In the CMS Microstrip Tracker the algorithms that are used for the online track reconstruction, require the alignment of the tracker modules on a level of better than 100 μ m . A Laser Alignment System has been developed that is able to detect possible movements or deformations of the Tracker mechanical structure with this level of precision. This system works with infrared laser beams which are detected by the silicon microstrip sensors, allowing to monitor movements of a subset of the tracker modules with respect to each other. In this article an overview of the Laser Alignment System is given, and first measurements with the integrated system are presented. The system has been shown to work properly and it confirms the expected mounting precision of the sensor modules in the detector endcaps. During cooling cycles no significant deformation of the endcap structure was observed.

The CMS Tracker alignment strategy

CMS Silicon Tracker alignment consists of three key components: survey during Tracker construction, measurements with the Laser Alignment System during operation and track based alignment. Methods and results are explained in detail, with a special focus on track based alignment due to its enormous complexity and numerical challenges.

The optical alignment system of the ZEUS microvertex detector

The laser alignment system of the ZEUS microvertex detector is described. The detector was installed in 2001 as part of an upgrade programme in preparation for the second phase of electron–proton physics at the HERA collider. The alignment system monitors the position of the vertex detector support structure with respect to the central tracking detector using semi-transparent amorphous-silicon sensors and diode lasers. The system is fully integrated into the general environmental monitoring of the ZEUS detector and data has been collected over a period of 5 years. The primary aim of defining periods of stability for track-based alignment has been achieved and the system is able to measure movements of the support structure to a precision around 10 μ m .

A laser shaft alignment system with dual PSDs

Shaft alignment is an important technique during installation and maintenance of a rotating machine. A high-precision laser alignment system has been designed with dual PSDs (Position Sensing Detector) to change traditional manual way of shaft alignment and to make the measurement easier and more accurate. The system is comprised of two small measuring units (laser transmitter and detector) and a PDA (Personal Digital Assistant) with measurement software. The laser alignment system with dual PSDs was improved on a single PSD system, and yields higher measurement accuracy than the previous design, and has been successful for designing and implements actual shaft alignment. In the system, the range of offset measurement is ±4 mm, and the resolution is 1.5 μm, with accuracy being less than 2 μm.

Laser alignment system for helical pinhole SPECT

Pinhole single photon emission computed tomography (SPECT) is very sensitive to mechanical alignment because it is a magnifying geometry. Because of magnification, small mechanical shifts of the aperture result in a large change in the projection data. Helical orbits may be used for pinhole SPECT to improve the completeness of the projection data. This has been done by using a research scanner to provide rotation while a linear stage produces axial movement. The combined effect is a helical orbit. However, reconstruction quality may be limited by the alignment of the linear stage with the axis of rotation of the scanner. We have developed a laser system for aligning the linear stage. We present the system design and estimate the accuracy of its alignment. Experimental helical pinhole SPECT data are presented.