Difference between revisions of "Holding Field Control"

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== Coil Current Control ==
+
 
 +
== Field Rotation GUI ==
 +
 
 +
The field rotation code is saved at[[Image:field_rotation.png|thumb|Window for Field Rotation]]:
 +
 
 +
  C:\AyeD\VI\Field Rotation\3D_Rotation_v4.vi
 +
 
 +
Before rotate the field, make sure the following condition satisfied:
 +
 
 +
# Target ladder is not moving;
 +
# Lasers are OFF;
 +
# No other target events are running (EPR, NMR, current calibration and etc.)
 +
# Because the timing is controlled softwarely by the computer, so close all other unnecessary programs and windows
 +
 
 +
To rotate the field to a desired direction:
 +
 
 +
# Find the code and '''run''';
 +
# Check current magnetic field direction:  a green line in the figure;
 +
# In the '''Destination''' panel, select the desired direction;
 +
# Hit '''Load''' button. The desired direction will be marked in red;
 +
# Check the field strength input and set it to '''25''' Gauss;
 +
# Check the rotation speed is '''1''' degrees per step;
 +
# Press '''Start Rotation/Ramping''' button, then hit '''Go ahead''' button;
 +
# Wait until rotation finishes. If success, both the '''Field Match''' and '''Angle Match''' lights are ON.
 +
# Make a Halog entry.
 +
 
 +
  If wrong direction is selected, do not panic because the field rotation/ramping can be
 +
  stopped by pressing the '''Emergency STOP''' button. Please go to correct direction afterward.
 +
 
 +
== Coil Control Hardware ==
  
 
=== Vertical Coil ===
 
=== Vertical Coil ===
Line 81: Line 110:
 
=== Horizontal Coils ===
 
=== Horizontal Coils ===
  
 +
== Holding Field and Coil Current Relations ==
  
 +
=== Longitudinal Compass Calibrations ===
  
−
== Holding Field and Coil Current Relations ==
+
==== January 5, 2009 ====
 +
 
 +
Survey Report:
 +
* [http://hallaweb.jlab.org/news/minutes/Survey_Reports/DT_A1207.doc DT_A1207.doc]
 +
Halog:
 +
* [http://hallaweb.jlab.org/halog/log/html/0901_archive/090105091105.html 090105091105.html]
 +
* [http://hallaweb.jlab.org/halog/log/html/0901_archive/090105125530.html 090105125530.html]
 +
 
 +
==== February 5, 2009 ====
 +
 
 +
Survey Report:
 +
* [http://hallaweb.jlab.org/news/minutes/Survey_Reports/DT_A1218.doc DT_A1218.doc]
 +
Halog:
 +
* [http://hallaweb.jlab.org/halog/log/html/0902_archive/090205114142.html 090205114142.html]
 +
* [http://hallaweb.jlab.org/halog/log/html/0902_archive/090205135420.html 090205135420.html]
 +
 
 +
==== April 07, 2009 ====
 +
 
 +
Survey Report:
 +
* [http://hallaweb.jlab.org/news/minutes/Survey_Reports/DT_A1226.pdf DT_A1226.pdf]
 +
Halog:
 +
* [http://hallaweb.jlab.org/halog/log/html/0904_archive/090407142646.html 090407142646.html]
 +
* [http://hallaweb.jlab.org/halog/log/html/0904_archive/090407205552.html 090407205552.html]
 +
* [http://hallaweb.jlab.org/halog/log/html/0904_archive/090409203758.html 090409203758.html]
 +
 
 +
==== June 18, 2009 ====
 +
 
 +
Survey Report:
 +
* [http://hallaweb.jlab.org/news/minutes/Survey_Reports/DT_A1233.doc DT_A1233.doc]
 +
Halog:
 +
* [http://hallaweb.jlab.org/halog/log/html/0906_archive/090617142239.html 090617142239.html]
 +
* [http://hallaweb.jlab.org/halog/log/html/0906_archive/090617150623.html 090617150623.html]
 +
* [http://hallaweb.jlab.org/halog/log/html/0906_archive/090618104742.html 090618104742.html]
  
 
== Gradient of holding field & Correction Coils ==
 
== Gradient of holding field & Correction Coils ==
Line 90: Line 153:
 
for longitudinal direction:
 
for longitudinal direction:
 
     0.982[(0.056-0.424+I_l)/(0.101+0.291+I_s)]= tan(37.0508)
 
     0.982[(0.056-0.424+I_l)/(0.101+0.291+I_s)]= tan(37.0508)
−
for longitudinal direction:
+
for transverse direction:
 
     0.982[(0.056-0.424+I_l)/(0.101+0.291+I_s)]= tan(127.0508)
 
     0.982[(0.056-0.424+I_l)/(0.101+0.291+I_s)]= tan(127.0508)
 
for vertical direction:
 
for vertical direction:
Line 109: Line 172:
 
the eigenvalue of the gradient matrix. Then use following numerical formula to get the current in each correction coil.
 
the eigenvalue of the gradient matrix. Then use following numerical formula to get the current in each correction coil.
 
<pre>
 
<pre>
−
     for correction coils along small coil: I=-0.342675967026 * dBz/dz
+
     for correction coils along small coil: I=-0.0342675967026 * dBz/dz
−
     for correction coils along large coil: I=-1.327674624226 * dBx/dx
+
     for correction coils along large coil: I=-0.1327674624226 * dBx/dx
 
</Pre>
 
</Pre>
 
here and below we will use so-called coil-system, which is shown below :
 
here and below we will use so-called coil-system, which is shown below :
Line 117: Line 180:
 
The current we use:
 
The current we use:
 
<pre>
 
<pre>
−
     current in small coil: 5.1699340 A
+
     current in small coil: 5.1699340 A   dBz/dz = -1.9151
−
     current in large coil: 4.7192990 A
+
     current in large coil: 4.7192990 A   dBx/dx = -14.1165
 
</Pre>
 
</Pre>
 
The gradient without correction coil: (in mG/cm)
 
The gradient without correction coil: (in mG/cm)
Line 147: Line 210:
 
The current of correction coils should be:
 
The current of correction coils should be:
 
<pre>
 
<pre>
−
     current in correction coils along small coil: 0.26284 A
+
     current in correction coils along small coil: 0.26284 A   dBz/dz = -7.6702
−
     current in correction coils along large coil: 1.10504 A
+
     current in correction coils along large coil: 1.10504 A   dBx/dx = -8.3231
 
</Pre>
 
</Pre>
  
Line 165: Line 228:
 
The currents of correction coils should be:
 
The currents of correction coils should be:
 
<pre>
 
<pre>
−
     current in correction coils along small coil:  A
+
     current in correction coils along small coil:  0.41020711984781 A     dBz/dz = -11.9707
−
     current in correction coils along large coil:  A
+
     current in correction coils along large coil:  0.25867084703795 A     dBx/dx = -1.9483
 
</Pre>
 
</Pre>
  
−
=== transverse field with BigBite off===
+
=== transverse field with BigBite on===
 
The current we use:
 
The current we use:
 
<pre>
 
<pre>
−
     current in small coil: 4.0849622 A
+
     current in small coil: -4.2409209 A
−
     current in large coil:  -5.6844599 A
+
     current in large coil:  5.5690744 A
 
</Pre>
 
</Pre>
 
The gradient without correction coil: (in mG/cm)
 
The gradient without correction coil: (in mG/cm)
 
<pre>
 
<pre>
 
                               dBx/dx      dBy/dy    dBz/dz      dBy/dx      dBz/dx      dBz/dy
 
                               dBx/dx      dBy/dy    dBz/dz      dBy/dx      dBz/dx      dBz/dy
−
average in pumping chamber:  1.678019   -3.399559   1.721540    10.623624   -12.601686   -5.303687
+
average in pumping chamber:  -5.901919   -7.173276   13.075196   -12.633972   0.479649  7.237270
−
average in target chamber: -4.639214   -10.318481  14.957695    0.601040   -14.587122   -1.811398
+
average in target chamber:   -4.727255   -12.117619  16.844874   -2.684100   -11.81095  4.831250
  
 
</pre>
 
</pre>
 
The current of correction coils should be:
 
The current of correction coils should be:
 
<pre>
 
<pre>
−
     current in correction coils along small coil: -0.26284 A
+
     current in correction coils along small coil: 0.52756678503488 A       dBz/dz = -15.3955
−
     current in correction coils along large coil: -1.10504 A
+
     current in correction coils along large coil: 0.52210804597687 A       dBx/dx = -3.9325
 
</Pre>
 
</Pre>
 +
 +
=== vertical field with BigBite on===
 +
The current we use:
 
<pre>
 
<pre>
 +
    current in small coil: -0.424 A
 +
    current in large coil:  0.409 A
 +
    current in vertical coil: -14.0 A
 +
</Pre>
 +
The gradient without correction coil: (in mG/cm)
 +
<pre>
 +
                              dBx/dx      dBy/dy      dBz/dz      dBy/dx      dBz/dx      dBz/dy
 +
average in pumping chamber:  -7.751536  1.251913    6.499623    -3.936450  -10.236216  -12.978525
 +
average in target chamber:  -16.516937  17.250368  -0.733431  -13.859642  -12.631008  -8.150575
  
 
</pre>
 
</pre>
−
 
+
The current of correction coils should be:
−
== Field Roation GUI ==
+
<pre>
 +
    current in correction coils along small coil:  A      dBz/dz = 9.1670
 +
    current in correction coils along large coil:  A      dBx/dx = 22.3719
 +
</Pre>
 +
<pre>
 +
By the way, the power supply of our correction coil is located in the middle room, counting house.
 +
The one labeled as loop 2 is for the correction coil in small coil direction,
 +
the other one labeled as loop 3 is for the large coil direction.
 +
</pre>

Latest revision as of 10:29, 25 July 2012

This is to discuss controling holding field of Polarized He3 Target with Helmholtz coils and correction coils.

Introduction

Target Coil System in the Hall

Holding field is created by three orthognal Helmholtz coils. As shown here, the small and large coils are creating uniform magnetic field in horizontal directions and the vertical coil is for a vertical holding field. Since the fields from these three coils are orthognal to each other, a Coil System is defined.

In the configuration of Transveristy experiment, the coil system is rotated 37 degrees from the Hall System. That is small coil pointing to the right downstream of the beam and large coil to the left downstream.

Characteristics of Hoilding Field Coils

Coil Name Radius (m) Turns Power Supply I(A) for 35 G U(V) for 35 G
Small 0.667 256 KEPCO 10 35
Large 0.758 272 KEPCO 10 35
Vertical 0.946 203 HP6675A 18 49


Field Rotation GUI

The field rotation code is saved at
Window for Field Rotation
: 
 C:\AyeD\VI\Field Rotation\3D_Rotation_v4.vi

Before rotate the field, make sure the following condition satisfied:

  1. Target ladder is not moving;
  2. Lasers are OFF;
  3. No other target events are running (EPR, NMR, current calibration and etc.)
  4. Because the timing is controlled softwarely by the computer, so close all other unnecessary programs and windows

To rotate the field to a desired direction:

  1. Find the code and run;
  2. Check current magnetic field direction: a green line in the figure;
  3. In the Destination panel, select the desired direction;
  4. Hit Load button. The desired direction will be marked in red;
  5. Check the field strength input and set it to 25 Gauss;
  6. Check the rotation speed is 1 degrees per step;
  7. Press Start Rotation/Ramping button, then hit Go ahead button;
  8. Wait until rotation finishes. If success, both the Field Match and Angle Match lights are ON.
  9. Make a Halog entry.
 If wrong direction is selected, do not panic because the field rotation/ramping can be 
 stopped by pressing the Emergency STOP button. Please go to correct direction afterward.

Coil Control Hardware

Vertical Coil

Vertical Coil is controlled in constant current mode by Power supply 6675A. In addition, there is a DS345 (GPIB Address 14) providing a control voltage to 6675A. Vertical coil current is baseline current set in 6675A plus a shift proportion to the control voltage.

  • 6675A Baseline current is set by GPIB command CURR Base Line Current
  • DS345 control voltage is set by GPIB command OFFS Control Setting

A calibration is performed on Sept 23, 2008. With Base Line Current=15A and 16A. Error is on the 0.1% level.

File:Vertical Coil Curr vs Setting.png
Calibration Data: Data Points are marked by circles and linear fitting is solid line. Red marks data with Base Line Current=15A, while blue mark Base Line Current=16A
  • Base Line Current=15A Result:
     model:
       ''Control Setting''= a + b*''Coil Current''
     Coefficients (with 95% confidence bounds):
       a =      -2.652  (-2.654, -2.651)
       b =      0.1767  (0.1766, 0.1769)
  • Base Line Current=16A Result:
     model:
       ''Control Setting''= a + b*''Coil Current''
     Coefficients (with 95% confidence bounds):
       a =      -2.828  (-2.831, -2.826)
       b =      0.1767  (0.1765, 0.1769)
  • Further, it's reasonable to a extrapolation by assuming coefficient b in unrelated to Base Line Current: 
       ''Control Setting''= 0.1767*(''Coil Current''-''Base Line Current'')
  • According to vertical compass work which was done on Sep 27, to get vertical field, the currents are
     I_v = 16 A
     I_s = -0.370 A
     I_l = 0.345 A

Horizontal Coils

Holding Field and Coil Current Relations

Longitudinal Compass Calibrations

January 5, 2009

Survey Report:

Halog:

February 5, 2009

Survey Report:

Halog:

April 07, 2009

Survey Report:

Halog:

June 18, 2009

Survey Report:

Halog:

Gradient of holding field & Correction Coils

Based on our compass measurement, we exactly know the relationship between current and direction. 

for longitudinal direction:
    0.982[(0.056-0.424+I_l)/(0.101+0.291+I_s)]= tan(37.0508)
for transverse direction:
    0.982[(0.056-0.424+I_l)/(0.101+0.291+I_s)]= tan(127.0508)
for vertical direction:
    General Equation is
      K[(I_v + E + BB)/sqrt{R*R(I_l+beta+delta)^2 +(I_s+ alpha+gamma)^2}]
    where
      K=0.546212 +/- 0.0022 and E= 0.176966 +/- 0.0354  for BigBite is off
      K= 0.552358 +/- 0.0022 and BB= 0.500829 +/- 0.034 for BigBite is on

On the other hand we need the amplitude of combined field to be about 25 Gauss, such as 

    I_l^2 + I_s^2 = 49    for in-plane case
    I_v = 14 A            for vertical case

In each case, we have 2 equations and two variables. So we can determine the currents for each direction and take them into our field mapping data, choose the one of two settings which has less gradient. To choose the gradient made by correction coil, we use a code on matlab to minimize the eigenvalue of the gradient matrix. Then use following numerical formula to get the current in each correction coil. 

    for correction coils along small coil: I=-0.0342675967026 * dBz/dz
    for correction coils along large coil: I=-0.1327674624226 * dBx/dx

here and below we will use so-called coil-system, which is shown below : Coil cor.gif

longitudinal field with BigBite off

The current we use: 

    current in small coil: 5.1699340 A    dBz/dz = -1.9151
    current in large coil: 4.7192990 A    dBx/dx = -14.1165

The gradient without correction coil: (in mG/cm) 

                              dBx/dx      dBy/dy     dBz/dz       dBy/dx      dBz/dx      dBz/dy
average in pumping chamber: -6.593216   -6.993122   13.586337   -10.687164   4.486893   -0.722354
average in target chamber:  -5.022424   -16.447674   21.470098   -0.880998   -6.230476  -1.056020

The currents of correction coils should be: 

    current in correction coils along small coil: 0.483739 A
    current in correction coils along large coil: 0.254263 A

transverse field with BigBite off

The current we use: 

    current in small coil:  4.0849622 A
    current in large coil: -5.6844599 A

The gradient without correction coil: (in mG/cm) 

                              dBx/dx      dBy/dy     dBz/dz       dBy/dx      dBz/dx      dBz/dy
average in pumping chamber:  1.678019   -3.399559   1.721540    10.623624   -12.601686   -5.303687
average in target chamber:  -4.639214   -10.318481  14.957695    0.601040   -14.587122   -1.811398

The current of correction coils should be: 

    current in correction coils along small coil: 0.26284 A    dBz/dz = -7.6702
    current in correction coils along large coil: 1.10504 A    dBx/dx = -8.3231

longitudinal field with BigBite on

The current we use: 

    current in small coil: -3.7947230 A
    current in large coil: -5.8821831 A

The gradient without correction coil: (in mG/cm) 

                              dBx/dx      dBy/dy     dBz/dz       dBy/dx      dBz/dx      dBz/dy
average in pumping chamber:  1.967711   -3.252200   1.284489     6.697551   -14.441990   3.611236
average in target chamber:  -4.359505   -6.263064   10.622569   -1.467912   -19.770538   4.559035

The currents of correction coils should be: 

    current in correction coils along small coil:  0.41020711984781 A      dBz/dz = -11.9707
    current in correction coils along large coil:  0.25867084703795 A      dBx/dx = -1.9483

transverse field with BigBite on

The current we use: 

    current in small coil: -4.2409209 A
    current in large coil:  5.5690744 A

The gradient without correction coil: (in mG/cm) 

                              dBx/dx      dBy/dy     dBz/dz       dBy/dx      dBz/dx      dBz/dy
average in pumping chamber:  -5.901919   -7.173276   13.075196   -12.633972   0.479649   7.237270
average in target chamber:   -4.727255   -12.117619  16.844874   -2.684100   -11.81095   4.831250

The current of correction coils should be: 

    current in correction coils along small coil: 0.52756678503488 A       dBz/dz = -15.3955
    current in correction coils along large coil: 0.52210804597687 A       dBx/dx = -3.9325

vertical field with BigBite on

The current we use: 

    current in small coil: -0.424 A
    current in large coil:  0.409 A
    current in vertical coil: -14.0 A

The gradient without correction coil: (in mG/cm) 

                              dBx/dx      dBy/dy      dBz/dz       dBy/dx      dBz/dx      dBz/dy
average in pumping chamber:  -7.751536   1.251913    6.499623    -3.936450   -10.236216   -12.978525
average in target chamber:   -16.516937  17.250368  -0.733431   -13.859642   -12.631008   -8.150575

The current of correction coils should be: 

    current in correction coils along small coil:  A       dBz/dz = 9.1670
    current in correction coils along large coil:  A       dBx/dx = 22.3719

By the way, the power supply of our correction coil is located in the middle room, counting house. 
The one labeled as loop 2 is for the correction coil in small coil direction, 
the other one labeled as loop 3 is for the large coil direction.
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