Technical report on the mapping of the magnetic field for the
Contents
1. and for the back shim coil system on output 2 Again it is important to set the power supplies to current mode The appendix contains an extract of the Agilent user manual where this is explained in great detail Appendix l The currents in the shim coils for which the B field is along the direction of the gravity in the center of the LH2 target Left shim 0 21 0 05A Back shim 0 35 0 05 A Right shim 0 5 0 05A Front shim 0 7 0 001 A Me Atogo Range ae Jo oT o 888e Locas MRE MALO Da Ea En 2 mann mann Agilent 3 Toe Fee Fic Gall 2 21 DE nu ne nm Agilent 2 Figure 10 Agilent power supplies To determine the sign of the displayed current the output plugs have to be checked Figure 10 Red connected to positive current Red connected to negative current 3 Remote control of Power suuplies The Danfysik power supply and the Agilents can also be controlled through the PC There are separate reports on the wiki how this can be done The control programs THe VI s are on the COMPAQ PC that also performs the magnetic field readout The BK precision power suppply cannot be remotely controlled To enable power supply settings or to readout the magnetic field the user has to login first Usually the labuser account should be used with the password fpiAy2__ note the two unserscore signs at the end The administrator account is called myadmin and has the password npdgRoot__ but a2. the front has to be pressed Figure 6 to actually turn on the main power supply After the polarity has been set to the big wheel on the left of the front panel can be used to adjust the set point Three different settings for the changing speed of the current are available coarse medium and fine Increasing the set point requires some patience because the power supply needs time to adjust to the new setting The display shows the current setting and the ready light flashes green as soon as the increasing can be continued Figure 7 The ideal set point has been found to be 920000 for a design magnetic field of 9 4 Gauss For this set point the output current is 23 A This setting will be optimized once the spin flipper is used Figure 5 Black switch at back of DANFYSIK Figure 6 Main power button DANFYSIK Figure 7 change of setpoint The next step is to turn on the BK Precision power supply This is done by setting the power switch to I and pressing the output button inwards Figure 8 To set the power supply to current mode the voltage has to be increased to the maximum followed by a current decrease until the red light in the current display CC lights up Now the current can be set The ideal current setting has been found to be 3 34 The lower limit of the Fine tuning knob for which the current is still 3 3 A has to be chosen The resistance of the coils changes with the time because they start to heat up Set the volta
3. the gravity and therefore the floor should not be used as reference Instead the centre of the polarizer which lies on the beam can be found Figure 13 With the help of a laser the beam height can be transferred from the polarizer to the left wall Figure 14 Now it is possible to measure the height of the flux gates relative to the beam level without measuring the distance to the floor This is done by placing a laser at flux gate height pointing towards the left wall where the beam height is marked 10 Figure 13 Position of beam marked on polarizer Figure 14 Laser sitting on stand and indicating height Although there are two flux gate sensors available and both measuring stands are designed to support both sensors it is not necessary to use them both at the same time Fluxgate 654 has two little feet which sometimes make it difficult to level it relative to the surface of the Aluminum table Figure 15 when the feet are in contact with this surface and the screws are pressing from the top of the flux gate Figure 15 Flux gate 654 Choice of stand for setup Depending on the orientation and direction of the measurement the stand is chosen For the gradient measurement the plate stand is the better choice since it can be leveled more accurately There are adjustment possibilities in three different spots and two little bubble levels are attached on top of the stand 11 Figure 16 Plate stand with one sensor inside Rem
4. the main power supply DANFYSIK Figure 2 The auxiliary coils are connected to the BK Precision power supply Figure 3 The inter connection between the coils is presented in figure 1 BK Precision Man Power Supply aux power Top guide coils en E Middle upper coils Middle lower coils Bottom lower coils Aux Power Supply BK Main Power Supply Precision Figure 1 Guide coil inter connection 2 How to turn on the power supplies The guide coils and the compensation coils are operated by two different power supplies The two power supplies are presented in figures 2 and 3 Figure 2 DANFYSIK power supply Figure 3 BK Precision power supply 2 1 How to turn on the guide coils The DANFYSIK power supply requires water cooling therefore the first action is to turn on the water cooler This is done by switching the orange power button of the later to I Figure 4 You can check the water level either on the instrument seen on the right side of Figure 4 or by looking into the water inlet at the top of the cooler or by just looking at the water flow meter shown in Figure 4 right that is installed in the water line Figure 4 water cooler left and water flow meter right Ideally the DANFYSIK is turned on after the cooler has been running for a few minutes Then the black switch on the back of the power supply can be pressed Figure 5 After this has been done the main power button at
5. Technical report on the mapping of the magnetic field for the NPDGamma experiment at FNPB at the Spallation Neutron Source ORNL Jasmin Schaedler Septimiu Balascuta Stefan Baessler Oak Ridge 08 20 2010 updated in February 2011 Contents 1 The electrical connection of the guide COI S ccccoooncnnnonacnnnnnnnanonnnonanonononanonnnnnronnnnnnronnnnnanoss 4 2 How to turn ON the power SUPHIICS ccseecccccssecccecssececeeesecececsueececeueecceceueceseuseceeseueeeeesagaeeeseas 5 2 1 How to turn ON the guide coils sossenesseenessseesssrrrsserrssssrrresseerssssrressrrersseresserrssseeesserreeseerrssseeeee 5 2 2 How to turn on the compensation COIS uesssesseessnensnessnnnsnnsnnnnnnnnnnnnnnnensnnnnnennnennessnnnnennen 7 3 Remote control of Power suuplies ussnnceeessssseseesennenennnnnnnennnnnnnennnnnnnnnnnnnnnnnnnnnnnnnnnnsnnssnnnsnnnsssnnnennen 9 4 Measuring the magnetic field with the flux gate sensors cccccoocccnncnnocnnnnnonacnnnnnnanonononaronenonnnnnonos 9 5 BAceliracv OF Measurement innatas ee dicta 13 1 The electrical connection of the guide coils There are four horizontal guide coils in the NPDGamma experiment There are a total of 36 2 1 39 main windings in the bottom and top guide coils and 21 2 1 18 main windings in each of the two middle coils In addition there are 12 auxiliary windings laid over each of the four main windings The main coils are connected in series to
6. ark The leveling has to be checked after each change in position since the iron floor in the cave is not perfectly flat The rail stand is used for all the horizontal measurements because it can be easily attached to one of the long rectangular extrusion rails Figure 17 Figure 17 Rail stand attached to extrusion rail Although this setup is convenient for horizontal changes vertical changes are a little bit more difficult To change the height supports of the wished height have to be shimmed at both ends In Figure 17 this was done with extrusion rails and to control the leveling of the rail the wood wedges were pushed in between The leveling is indicated by the bubble level located on the bottom wall of 12 the Aluminum case with two compartments where both the two sensors can be fixed simultaneously with plastic screws 5 Accuracy of measurements All the distance measurements are done with the Leica DISTO D330i distance laser Appendix Il a caliper or a measuring tape Laser accuracy 1mm Measuring tape accuracy 1 6 1 6mm Caliper accuracy 1mm The leveling is done with bubble levels Leveling accuracy 0 02 0 00035rad Appendix Ill contains calibration certificates for both flux gates Flux gate sensors accuracy The misalignment of the three sensors for the Flux gate 654 MAG2 are X 1 0 0022 radians Y 1 0 0034 radians Z 1 0 003 radians The misalignement for the three sensors inside the Fluxgat
7. d flux gate 654 is sensor two this order should not be changed x man vos AA RN E m SS m A Deir E A A E E TEE ln HS ERNE a q AGR ee oS I mitra Mex aer s near HO E BA H TEIR h ge fi scan type not yet i ONG MESSU ETHET tomat Karning Com 6 7 DAG Fella S hs Cuna lm Beer I E a eee i ant z 0 1480 amp 0 4700 E E NO Figure 12 LabView program window To stop a data run the blue button has to be pressed again followed by the red Close button The collected data can be found on hard drive C in the folder data Every time a new run is started a new text file is created and named with date and starting time To export the data to another computer a LAN connection has to be established This is the only available option because there is no wireless reception in the cave and the USB port of the computer does not work If the user inserts a memory stick in any USB port will determine the Windows operating system to shut down and to try to reboot from the memory drive that was inserted in the USB port Positioning of the flux gate sensors Since we know the distance from between the guide coil centre and the beam guide flange 98 05 249 05cm this distance is marked on the coil frame with yellow tape and is used as reference point Another important distance is the beam height Due to the heavy beam stop the steel plates on the floor are not perfectly leveled relative to the direction of
8. e 557 MAG1 X 2 0 00096 radians Y 2 0 0023 radians Z 2 0 00025 radians The offset of the sensors are the fields read by the three sensors when the probe is placed in zero magnetic field The offset fields are given in the calibration certificate for both fluxgates Fluxgate 557 X1 3 5 nT Y1 10 5 nT Z1 3 5 nT Fluxgate 654 X2 6 5 nT Y2 0 Z2 10 5 nT 13 Appendix
9. ge limit to a very high number it is important to keep the power supply in current mode so that the current stays constant The accuracy of the BK Precision is very limited but good enough for the experiment a change in the BK Precision current of 0 1A can be tolerated but should be avoided Output button ZA WARNING Do not operate unit Remote Sense mo without proper four wi connections Damage ci occur lo power supply unit under test gt Main A Figure 8 BK Precision power supply 2 2 How to turn on the compensation coils Additionally to the guide coils compensation coils have to be used since the magnetic field is distorted by several factors like the shielding or the polarizer compensation magnets Figure 9 The coil stand in the cave parts of the back and the right shim coil system are marked red There are four shim coil systems one in the back downstream close to the Beam Stop n 37 one in the front upstream n 37 one to the left beam left n 28 and one to the right beam right n 28 They are located on the outer side of the coil stand Figure 9 is trying to give an idea of the shim coil positions The compensation coils are operated by two Agilent power supplies with two outputs each Agilent 2 F218734 provides power for the right shim coil system on output 1 and for the front shim coil system on output 2 Agilent 3 F218735 provides power for the left shim coil system on output 1
10. s usually shouldn t be used unless necessary On the desktop the user finds the folder NPDG_Remote It contains the files ag2 vi This labview program controls the Agilent power supplies See the separate report df2 vi This labview program controls the Danfysik power supply See the separate report fg2new vi This labview program reads the fluxgates See next chapter 4 Measuring the magnetic field with the flux gate sensors First the DAQ Module has to be turned on this is done by moving the little lever to On Figure 11 MAG O3DAM MMMM Daraacau s ronmopuLe BATTERYSTATUS ON Oo O So POWER RECHARGE ILLUMINATE OFF N WARNING mur Bartington TO MAXIMISE BATTERY LIFE WHE WHEN BATTERY instrumenti OXFORD MOL AND SWITCH OFF POWER WHEN NOT IN USE ILLUMINATED ISCHARGING Figure 11 DAQ Module for flux gate sensors To display the measurements the LabView program has to be started on the computer The user has to open the folder NPDG_Remote located on the desktop and then click the LabView program fg2new vi After the program has been opened the LabView run button white arrow has to be pressed followed by the green button that says click to run driver After a few seconds the sign NOT SIGNED ON will change to SIGNED ON and the blue button click here to start scanning has to be clicked to start the data acquisition Figure 12 LabView displays the data for two flux gate sensors Flux gate 557 is sensor one an
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