UBC Undergraduate Research

Nuclear magnetic resonance field stabilization Bycraft, Brad; Herzog, Kyzyl Jan 15, 2012

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
52966-Bycraft_B_et_al_ENPH_479_2012.pdf [ 911.32kB ]
Metadata
JSON: 52966-1.0074489.json
JSON-LD: 52966-1.0074489-ld.json
RDF/XML (Pretty): 52966-1.0074489-rdf.xml
RDF/JSON: 52966-1.0074489-rdf.json
Turtle: 52966-1.0074489-turtle.txt
N-Triples: 52966-1.0074489-rdf-ntriples.txt
Original Record: 52966-1.0074489-source.json
Full Text
52966-1.0074489-fulltext.txt
Citation
52966-1.0074489.ris

Full Text

                                                                                                                           NUCLEAR MAGNETIC RESONANCE FIELD STABILIZATION    Brad Bycraft Kyzyl Herzog                                                                                                                                                                                                         Project Sponsor: Carl Michal   Engineering Physics 479 Faculty of Applied Science The University of British Columbia January 15th, 2012   Project Number 1254     ii  EXECUTIVE SUMMARY  Earth?s Field NMR involves very sensitive magnetic fields that must be held static for experiments to succeed. As part of a revamping of the introductory physics curriculum, UBC Physics plans to outfit a lab with a number of small EFNMR scanners that can be operated by students. Preliminary experiments conducted in the planned space have shown that there is significant DC field interference, most likely produced by the nearby elevators. Due to the low frequency of the interference, and the dynamics of elevator use throughout the day, an active field stabilization system is required if the EFNMR labs are to proceed as scheduled. The effort to realize a field stabilization system as outlined above is being funded by UBC Physics, with cooperation from the Engineering Physics Project Lab. Success will mean not only that the new EFNMR labs can proceed in the coming 2013 school term, but will also represent a unique solution to the problem of shielding a large volume of space from DC interference. One can find applications for such results anywhere requiring the simultaneous operation of many NMR scanners in close quarters. The details of the designed system may, therefore, be of enough merit to warrant a scientific publication detailing the process so that others may benefit from the work.      TABLE OF CONTENTS Executive Summary ........................................................................................................................ ii List of Figures ................................................................................................................................ iv List of Tables ................................................................................................................................. iv 1.0 Introduction .......................................................................................................................... 1 2.0 Discussion ............................................................................................................................ 2 2.1 Theory .............................................................................................................................. 2  2.1.1     AC Interference ................................................................................................ 3  2.1.2     DC Interference ............................................................................................... 3 2.2 Methods ............................................................................................................................ 4  2.2.1     Spatial Measurements ...................................................................................... 4  2.2.2     Temporal Measurements ................................................................................. 5  2.2.3     Gradient Measurements ................................................................................... 5 2.3 Apparatus ......................................................................................................................... 6 2.4 Results .............................................................................................................................. 7  2.4.1     Spatial Measurements ...................................................................................... 7  2.4.2     Temporal Measurements ................................................................................. 8  2.4.3     Gradient Measurements .................................................................................. 10 2.5 Discussion ...................................................................................................................... 11 3.0 Conclusions ........................................................................................................................ 13 4.0 Project Deliverables ........................................................................................................... 14 4.1 List of Deliverables ........................................................................................................ 14 4.2 Financial Summary ........................................................................................................ 14 4.3 On-going Commitments ................................................................................................. 15 5.0 Recommendations .............................................................................................................. 16 Appendix: Project Charter ............................................................................................................ 17      iv  LIST OF FIGURES  Figure 1. Spatial measurement system consisting of a rail and cart ............................................... 4 Figure 2. Magnetic field measurement cart for the spatial measurement system ........................... 5 Figure 3. Top view of the magnetic field measurement device ...................................................... 6 Figure 4. Sliding rail and slot for the QRD for consistent one-inch measurements along the rail . 7 Figure 5. Field disturbance (top) due to the arrival of one of the north elevator and (bottom) the baseline field map. There is a pronounced DC magnetic field being introduced by the arrival of the elevator. ..................................................................................................................................... 8 Figure 6. Dynamic/temporal response of the two elevators in the hallway of the Hebb building. . 9 Figure 7. Gradient map of Hebb 30, ranges from 1900 to 2250 mGa, in increments of 50mGa. 10 Figure 8. Gradient map of Hebb 31; ranges from 1900 to 2300 mGa, in increments of 50mGa. 10 Figure 9. Distribution of the field magnitude in each of Hebb30 and 31. Red lines indicate the mean field strengths of 2105mGa and  2047mGa, respectively. .................................................. 11      v  LIST OF TABLES  Table 1: Estimated elevator dipole parameters ............................................................................... 9 1   1.0 INTRODUCTION  Providing hands-on experience to undergraduate students in a lab environment is critical to developing a fundamental understanding of the material.  Providing context for learning also helps promote interest in the material and aids the ability for the students to learn effectively.  In PHYS 102, the majority of the students are in life sciences, and they plan to study medicine.  These students are not particularly interested in learning about electric circuits and magnetic fields.  To create context for this material into PHYS 102, the physics department is integrating nuclear magnetic resonance (NMR) imaging into the lab section of the course.  This will provide the students with some context for which they can learn about electric circuits and magnetic fields that is directly related to their career in medicine. To provide the students with their own NMR scanning machines, the physics department had to create their own devices.  These NMR scanners use the earth?s magnetic field to produce images.  Although these devices cost very little in comparison to purchasing a pre-made one, they are easily disrupted by external magnetic field changes. The objective of this project is to help understand and characterize the problem that affects the NMR scanners, and help allow the NMR scanners to be effectively used during the labs. In order to bring these NMR scanners into the lab without ruining the experiments, the magnetic field disturbances need to be characterized and minimized so the lab experiments can occur without be effected by external sources. This report provides details on the magnetic field disturbances that ruin experiments done by the NMR scanners.  Details on the collection of data, the analysis of data, and determination of the type of magnetic field are provided.  Solutions to the characterized problem will be briefly mentioned, but not detailed in this report. This report will contain a discussion of the theory behind the project, testing methods and equipment, and results.  A discussion of the results will follow that provides details of the magnetic field disturbance, potential errors, and limiting performance of the equipment.  The conclusion of the results and project deliverables will also be mentioned, followed by financials and recommendations for continuation of the project.      2   2.0 DISCUSSION  Nuclear Magnetic Resonance (NMR) is a method of analyzing a sample by detecting changes in the magnetic precession of hydrogen atoms (contained in the sample) as they are perturbed by the application of magnetic fields. Earth's Field NMR scanners use NMR techniques to scan a sample, but differ from conventional NMR-based methods, such as clinical MRI. EFNMR uses Earth's magnetic field (approximately 30-50?T in magnitude) as the main field relative to which the rest of the experiment is calibrated, where standard NMR scanners use superconducting magnets to produce high (3-21T) fields.  Thus, while significantly less complex in design and operation, EFNMR scanners are highly susceptible to interference from external fields. The sensitivity of NMR has prompted the development of numerous methods of shielding and compensation to counteract any interference and maintain experimental precision. Commonly used examples include simple Faraday cage shielding, local active compensation systems, and internal magnetic shimming (i.e. dynamically modifying the main field with small coils internal to the magnet).  Unfortunately, these methods are not always applicable to EFNMR.  Due to the extremely high main field traditionally used in NMR scanners, the majority of interference comes from high frequency oscillating magnetic fields, which are readily blocked with Faraday shielding.  EFNMR, however, operates with low main field, and thus is more sensitive to low frequency interference, which will easily bypass a Faraday cage.  Similarly, due to the low field strength involved, shimming would require shim coils that are both precise enough to shim the sensitive main field, but powerful enough to counteract a potentially strong and dynamic external DC field.  This is not a realistic requirement of a coil internal to the scanner.  Thus, an external active compensation system is the natural choice for EFNMR.   2.1 Theory  The principal task is to identify and characterize any major sources of magnetic interference that may be affecting the NMR experiments. Since the scanners are most sensitive to DC magnetic fields, the DC offset caused by the elevators requires the special attention, as do any static gradients across the sample being scanned. Additionally, it is possible for the scanners to pick up on AC signals, such as 60Hz harmonics from the power mains. Here we address these different types of magnetic interference and their effects on NMR/MRI scans.   3   2.1.1  AC Interference  The scanners are equipped with faraday enclosure, approximately one centimeter thick, which will readily disperse most AC fields, all the way down to the 60Hz signals found in power lines. Below 60Hz, however, the some waves will penetrate the cage, as this is where the skin depth is roughly one centimeter. Fortunately, the period of these waves is greater than the duration of each acquisition in the MRI sequence (a so-called ?filtered back-projection? scheme) by an order of magnitude. This means that for each individual acquisition the field appears to be roughly constant, so the spins in the sample will not lose coherence. Since there are many of these back projections averaged over a time much greater than the period of the interference, the final image will appear intact but will have some periodic noise superimposed. In other words, the low frequency fields that penetrate the faraday cage will impact the signal-to-noise ratio (SNR) of the acquisition, but will not destroy any spectral structure. Since the scans are for educational purposes only, compromising the SNR does not meaningfully impact the results.   2.1.2 DC Interference  Static (DC) magnetic interference is much more problematic for the scanners than AC fields, even those that penetrate the faraday shielding. A successful scan relies on the spins in the sample being aligned, and the spins are said to ?precess? with a frequency proportional to the earth?s field. Any DC field component present at the time of scanning will superimpose onto the baseline static field produced by the earth, causing a shift in the precession (a.k.a. resonant, a.k.a. Larmor) frequency. If the DC interference is constant in space and time, the scanner will simply be calibrated to the new resonant frequency. If, however, the interference appears after the scanner has been calibrated (such as an elevator moving past the lab), the scanner will transmit excitation pulses to the sample at the incorrect frequency, resulting in a very poor NMR signal. Another condition that has the potential to confound the scanning process is when there is a linear gradient across the sample being scanned. Such a field can produce two different effects. First, a linear gradient across the sample will affect the spins in the same way as a constant DC field does, except instead of the resonant frequency shifting over the entire sample, it becomes a function of position. This has the effect of ?slicing? the sample, so that only a small portion of the spins, whose resonant frequencies match with the frequency of the excitation pulse, yield an appreciable NMR signal. In fact, this is precisely the technique used to intentionally slice up 3-D volumes into a series of MRI images.  The other way which gradient fields can affect the scan is by moving the resonant frequency outside of the tuning range of the excitation coil entirely. This occurs at the extremes of the 4   gradient, or when the average magnitude is much different than the baseline field (~50uT). For low-bandwidth coils such as those used here, this can be a significant issue.  2.2 Methods  Testing can be broken up into three distinct regimes: 1. Identifying spatial distribution of DC fields near the labs. 2. Identifying temporal distribution DC fields near the labs.  3. Identifying DC field gradients within the labs. Although evidence was encountered that suggests that some AC fields may be influencing the scans, there was no protocol for direct measurements of those fields. 2.2.1 Spatial Measurements  For the spatial measurements, we designed a jig that would take measurements over a large span of the hallway.  The jig composed of a marked rail, with white and black tape at one inch intervals, and a moving cart that slid along the rail.  This set up would take a measurement every inch along the rail across the hallway.  From here, we marked one foot increments across the width of the hallway and took measurements at six increments along the hallway.  This gave us close to 2000 data points for the elevators in each position.  Figure 1. Spatial measurement system consisting of a rail and cart. 5    Figure 2. Magnetic field measurement cart for the spatial measurement system.  2.2.2 Temporal Measurements  The temporal measurements involved measuring the magnetic field at a particular place in the hallway as the elevators went from the main floor to the top floor.  To do these measurements, we timed the elevator ride a couple times to get a consistent time.  We then programmed the sensors to take measurements for 20 seconds (time of the elevator ride).  We tested the sensors in three different areas for each of the elevators and gathered over 1000 data points of dynamic changes to the magnetic field.  2.2.3 Gradient Measurements  The gradient measurements involved mapping out each one of the rooms, Hebb 30 and 31.  To do these measurements, we manually took measurements in a grid layout.  We measured the length and width of the rooms and then evenly divided between them to create a one-meter grid for the measurements.  This grid is smaller than the distance between the scanners and would provide an accurate map of the room.  For both rooms, about 200 data points were gathered to map the gradients.  6   2.3 Apparatus  All data were gathered via a custom made probe. The probe consists of a field sensor, a microcontroller, a Bluetooth transceiver, a reflectance sensor and supporting electronics. These components are mounted on a platform which can be carried freely, or mounted to a 16-foot aluminum rail for precise spatial positioning.   Figure 3. Top view of the magnetic field measurement device. The operation is as follows. The microcontroller is put into one of three modes: manual, spatial, or temporal. In manual mode, the controller simply instructs the sensor to obtain a measurement when the operator pushes a button. In the spatial mode, which is typically used when the probe is mounted on a rail, the microcontroller instructs the sensor to obtain measurements whenever the reflectance sensor fires. Attaching a regular black-white-black pattern to the rail allows this mode to obtain data on a fixed spatial grid. Finally, the temporal mode uses the microcontroller?s timers to gather measurements from the sensor separated by regular intervals of time. This allows characterization of the magnetic field through time.  7    Figure 4. Sliding rail and slot for the QRD for consistent one-inch measurements along the rail. Regardless of the mode of operation, the gathered data are transmitted wirelessly via Bluetooth back to a computer that acts as a governor for the whole setup, ensuring that all data are aligned and stored properly.  2.4 Results  Below are the main results of performing each of the testing protocols given in section 2.2.  2.4.1 Spatial Measurements   Given here are the summary results characterizing the spatial distribution of the hypothesized magnetic dipole produced by the elevator(s). Each field map is computed from the raw data by subtracting of the baseline map and removing known sampling artifacts. The baseline field map is defined to be the ambient field sensed when both elevators are far away from the probe; in this case, ?baseline? refers to the condition when both elevators are in the basement.   8    Figure 5. Field disturbance (top) due to the arrival of one of the north elevator and (bottom) the baseline field map. There is a pronounced DC magnetic field being introduced by the arrival of the elevator.   2.4.2 Temporal Measurements  Given here are the summary results characterizing the time evolution of the DC magnetic field surrounding Hebb30/31. Figure 6 shows the dynamic response as the elevators pass by the probe, which is fixed in one position. Many such measurements are used to fit simple dipole far-field models centered on each elevator.  9    Figure 6. Dynamic/temporal response of the two elevators in the hallway of the Hebb building. Fitting the temporal data to dipole fields travelling with the elevators yields two approximate magnetic dipoles principally oriented in the x-y (floor) plane. The larger north elevator produces a dipole moment inclined 105 degrees from the vertical, rotated 30 degrees azimuthally from the negative x-direction and having a strength of 14500A/m2. The dipole moment produced by the south elevator is similar in orientation, inclined 95 degrees by 15 degrees azimuthally, but has a dipole moment of 11300A/m2, roughly 20% smaller than that of the north elevator. The fitted parameters are reported in increments of 5 degrees and 100A/m2, as the estimates are believed to only be accurate within these bounds. Table 1: Estimated elevator dipole parameters. Elevator Incline Angle (deg) Azimuthal Angle (deg) Magnetic Moment (A/m2) North 105 30 14500 South 95 15 11300  10   2.4.3 Gradient Measurements  Below are magnetic contour maps of each of the two labs, Hebb30 and Hebb31, where the NMR experiments are to take place. The goal is to visualize the static gradients present in each lab, regardless of the effects of the elevators. As is evident from Figures 7-8 the field distribution is far from uniform, ranging from 1.9 Ga to 2.3 Ga in each room.   Figure 7. Gradient map of Hebb 30, ranges from 1900 to 2250 mGa, in increments of 50mGa.   Figure 8. Gradient map of Hebb 31; ranges from 1900 to 2300 mGa, in increments of 50mGa. 11    Figure 9. Distribution of the field magnitude in each of Hebb30 and 31. Red lines indicate the mean field strengths of 2105mGa and  2047mGa, respectively. Figure 9 gives the empirical distributions of the field magnitude in each lab. Again, a wide range of field strengths is present. However, the approximate field gradients are fairly gentle, only exceeding 200mGa/m in a few places. These results indicate that the scanners should be able to operate in the majority of the lab, but there are some areas where the field gradients may be too high, and/or the field strength is too far from the mean to be tuned to.  2.5 Discussion  Having an estimate of the strength and orientation of the magnetic dipole moment of each the elevators allows for further experimentation to attempt to verify and eliminate the disturbances. There are, however, a number of conclusions one can draw from the results themselves. First, the near-planar orientation of the dipole moments indicates that one could compensate for the fields by introducing a locally opposed dipole moment in the x-y plane. This would cancel the principal component of the effective dipoles produced by the elevators. The remaining z-component is likely not strong enough to introduce significant frequency shifting into scans taken a number of meters away from the source.   Second, the strength of the dipole moment(s) hints at several engineering challenges. In order to produce a dipole moment comparable to that of the north elevator one would require a significant power source. Using a simple 6? wound solenoid coil with an air core would require hundreds of amps of current. Introducing an annealed iron or steel core reduces this figure to less than 15A, a much more feasible target. Nevertheless, a 15A power supply would require direct access to the power mains (not necessarily possible from within an elevator) or multiple large batteries, given 12   that the experiments are set to run for many hours at a time. There are additional safety concerns associated with placing high current devices and large (likely lead-acid) battery banks in a public space.  Finally, the strength of the dipole moments produced by the elevators all but rule out using an active compensation system that does not travel with the elevators. Such a system would need to cancel the intrusive fields in real-time as they evolve, but it is highly unlikely that a large iron core would have a fast enough response time or a flat enough hysteresis curve to tune a stable control system. This all but rules out any real-time solution that does not work locally at the per-scanner level. Aside from the main results regarding the dipole fields, we can glean useful information from the measurements of the lab gradients and spatial distributions. As evidenced by figures 7 and 8, the gradients within the laboratories are rather gentle over short distances. If the typical gradient was less than 200 mGa/m, which corresponds to roughly a 40 mGa change over the length of the sample being scanned, this would be only a ~8% change field strength. This is not enough to induce significant slicing of the sample and, provided that the baseline field strength is near a typical value, will not push the resonant frequency outside of the tuning range of the scanner. Thus, the gradients only pose an issue on the scale of the whole lab, meaning that there may be select areas of the lab unsuitable for scanning, but on the whole any small gradients will be inconsequential or can be shimmed out by the scanner. The spatial field distributions also show some areas of significantly lower field than the average. Several of these measurements were localized to the space surrounding a large power distribution box, indicating that either the power lines are producing fields that are affecting the magnetic probe used to take measurements, or there is something present in the area causing a large field drop. The possibility of the probe being affected was tested by changing the magnetic sensor from one that measures cycles in a solenoid coil, which will easily couple with EM-noise, to an Anisotropic Magnetro-Resistive (AMR) solid state sensor. This switch saw a reduction in the field dropout, and in the measurement noise, suggesting that the solenoid sensor was indeed coupling with an external source. However, the fourier spectra of time series measurements show that the power is spread over a wider range than expected. It is possible that a large switching transformer in the power distribution box is responsible for the extra non-DC power, a hypothesis which is supported by the field dropout, given that most switching transformers contain large amounts of magnetic material. The net effect this has on our measurements remains unclear since we are unable to shut down the power box, but the effects do appear to subside quickly as the probe moves further away.     13   3.0 CONCLUSIONS  Having characterized the magnetic field in and around the labs where NMR experiments are set to take place, it is clear that a significant magnetic disturbance is being introduced by transient motion of the building elevators. Moreover, said disturbance appears to be over a relatively simple form, likely making compensation with conventional dipole electromagnets a feasible option. In that eventuality, the NMR experiments would be able to commence unimpeded in the 2013/2014 session.  While the analysis conducted concludes that direct compensation (i.e. cancellation) of the intruding magnetic field is feasible, the question of precisely how to do so remains open. Indeed, it is unclear that direct cancellation is even the correct solution. There are significant advantages to incorporating compensation technology into the scanners themselves, but to do so would require an additional monetary investment into the scanners and a large block of time to work out the engineering challenges.     14   4.0 PROJECT DELIVERABLES  This section of the report provides the list of deliverables, as well as the contrast to the initial deliverables, based on the project sponsor?s request.  A financial summary of the project is also provided, and the state of the team members? on-going commitments is mentioned briefly.  4.1 List of Deliverables  The final deliverables for the project were considerably different than the initial deliverables for the project.  Throughout the term, as the project progressed, meetings with the project sponsor revealed that more delving into more detail prior to implementing a canceling field would be beneficial.  The final deliverables ended up to focus heavily on characterizing the magnetic field due to the elevators.  This allows the project sponsor to take the data and look into more elaborate solutions, rather than rush and spend unnecessary money on a temporary solution.  Final Deliverables:  1. Characterize the magnetic field due to the elevators, as well as the dynamic field produced due to movement of the elevator. a. Characterize the magnetic field magnitude in the Hebb classrooms.  Both Hebb 30 and 31 need to be characterized as either room (or both) may be used for the experiments. b. Provide the code used to calculate the magnetic field calculations, specifically the dipole calculations.  Initial Deliverables:  1. Complete a system of sensors with a control system that will keep a field relatively constant on a room scale. a. The system should be adjustable for different locations (rooms/buildings). 2. Well documented source code that can be changed for future additions (another stabilization coil, new sensors). 3. One or more coils to stabilize the field produced due to the elevators. a. The maximum fluctuations should be ideally below 1 Hz (2 Hz is acceptable).  4.2 Financial Summary  All materials were provided by the Engineering Physics Project Lab and Carl Michal. To our knowledge no purchases were made on our behalf.  15   4.3 On-going Commitments  There are no on-going commitments for the project by any of the team members.   16   5.0 RECOMMENDATIONS  Having spent considerable to characterizing the magnetic phenomena surrounding the lab rooms in question, it is our opinion that the scanners should, if possible, be moved to a location that is further from potential disturbances such as elevators, power boxes and large structural members. In this regard, we recommend that the NMR experiments take place in an underground location, as is often chosen in NMR/MRI installations. This would eliminate the majority of AC and DC interferences, as well as likely move the scanners further from large concentrations of metal found in above-ground floors, likely improving the homogeneity of the spatial field distribution.  Barring the possibility of moving locations, we have two further recommendations.  1. Conduct a study to ascertain the feasibility of direct compensation of the dipole moments of the elevators. Our results show that this route is a possibility, but as already outlined there are numerous engineering challenges, and it remains unclear that a simple configuration of dipole coils is capable of keeping the frequency shifting of the scans under 2 Hz. This option represents the least complex solution and, depending on the precise implementation, has the potential to minimize material costs. Pay special attention to the safety issues related to this approach, as a carelessly implemented solution could halt the entire lab program.  2. Do not invest greater time and resources into the pursuit of a solution that involves real-time compensation of the elevator dipoles. Again, as outlined already, our results show that this would require a number of iron cored sources, which at high current are unlikely to have magnetic responses suitable for stable real-time system control.  Although there has been discussion with Carl Michal over the modification of the NMR scanners to include features that could compensate for the intrusive magnetic phenomena, such an endeavor would represent a significant re-engineering of the scanners and is thus an unattractive option. Moreover, a change to the scanners on this scale reaches far beyond the scope of this project and thus we can make no informed recommendation as to its merits or dangers.   17   APPENDIX: PROJECT CHARTER  Project Charter  -  APSC 459/479, Engineering Physics Project Lab  Project Number, Title: PN 1254, Magnetic Resonance Imaging Field Stabilizer  Project Summary: Develop a real-time active magnetic field compensation system to stabilize one or more classrooms that contain NMR lab experimentation equipment.  The system should be flexible so that the field can be adjusted based on the room(s) that needs to be shielded.    Start Date: Sept 13th, 2012 End Date: Dec 21st, 2012  Statement of Deliverables: 1. Complete a system of sensors with a control system that will keep a field relatively constant on a room scale. a. The system should be adjustable for different locations (rooms/buildings). 2. Well documented source code that can be changed for future additions (another stabilization coil, new sensors). 3. One or more coils to stabilize the field produced due to the elevators. a. The maximum fluctuations should be ideally below 1 Hz (2 Hz is acceptable).   Criteria for Success: With the completed system activated, the magnitude of the magnetic field at any position within the target classroom should fluctuate by less than 1 part in 2000 when the Hebb elevators are moved to any position.   Initial Budget Estimate and Source of Funds: $2000 provided by the sponsor (potentially from the course the field stabilizer is designed for).  Project Scope - Activities in Scope 1. Characterize field disturbances from elevator and surroundings. 2. Research sensors and core for coil. 3. Design & fabricate (or buy) the coil. 4. Design the control system.  Activities out of Scope 1. An easy to use GUI. 2. NMR interference measurements are not necessary. 3. Moving chairs for measuring/testing interference. Assumptions and Anticipated Risks The elevator is assumed to be the main source of magnetic interference. An anticipated risk is that there are other major sources of interference aside from the elevator.     18   Stakeholders:  Project Sponsors: Carl Michal Team Members: Kyzyl Herzog, Brad Bycraft  Project Lab: Other:  Communication and Meeting Schedule: Set meetings on Thursday from 12:15 ? 1:15pm with extended time as needed. Communication will be through email otherwise.   Other Issues: The main room is Hebb 30 and rooms 31 and 32 are secondary rooms to shield.  If there are other major interferences beside the elevator, just focus on shielding the field due to the elevator.  For a potential paper ? getting field measurements with and without the control system would be beneficial. Project Charter Sign-Off  Name/Date         Name/Date          Project Sponsor Project Sponsor   Name/Date         Name/Date        Name/Date        Name/Date                   Team Member 1 Team Member 2  Team Member 3 Project Lab   

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.52966.1-0074489/manifest

Comment

Related Items