Diff: MA7

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JSPWiki v2.0.52


Difference between version 58 and version 13:
Line 1 was replaced by line 1
- !!MA7
+ !!6.8 Tesla Horizontal Field Cryomagnet MA7
Line 3 was replaced by lines 3-15
- This new 6.8 Tesla horizontal field cryomagnet has strong stray fields due
+ The horizontal high field cryomagnet has a restricted neutron access.
+ There are 4 windows of 45 deg each, valid for a sample of 15 mm diameter.
+ For larger samples, the opening angle for full access is sligthly smaller.
+ In the field direction, the vertical access is +- 22.5, in fact, the access
+ is a cone. Perpendicular to the field direction, the access is +-6.7 deg on
+ a 15 mm sample, or 65 mm parallel access.
+
+ [MA7/MA7coils.png]
+
+ For access with polarized neutrons, an asymmetric mode (max. 6.2 Tesla)
+ is available. This is needed when a beam perpendicular to the field is used.
+
+ This cryomagnet has strong stray fields due
Line 8 was replaced by lines 20-24
- !Restrictions on RITA-II
+ [MA7 Specifications]
+
+ More information on intranet page (drawing): [LdmWiki:MA7]
+
+ [MA7 Restrictions]
Lines 10-11 were replaced by line 26
- Provisional force measuremnents on RITA-II have shown that
- the operation of MA7 on Rita-II is allowed:
+ [MA7/MA7pict.jpg]
Lines 13-67 were replaced by lines 28-58
- * between 3.0 and 18.0 meV (a2 >= 37 deg) at a distance of 450 mm or more, up to 4 Tesla
- * between 3.0 and 8.0 meV (a2 >= 56 deg) at a distance of 450 mm or more, up to 4.4 Tesla
- * between 3.0 and 8.0 meV (a2 >= 56 deg) at a distance of 540 mm or more, up to 5.5 Tesla
-
- For any other configuration force tests have to be done.
- As soon as the approriate adapter plate is avaliable, we should
- repeat the force measurments.
-
- Original data:
- ||a2 [[deg] || distance [[mm] ||field [[Tesla] || force [[N] || extrapolated field [[Tesla] for 500 N || allowed field with security margin
- | 56 | 540 | 4.8 | 230 | 6.8 | 5.5
- | 56 | 450 | 3.4 | 180 | 5.5 | 4.4
- | 37 | 450 | 3.4 | 220 | 5 | 4
-
- [MA15RitaRestrictions/SampleTableDistance.jpg]\\
- How the distance has to be measured.
- In this example the distance is around 400 mm.
-
- !Restrictions on AMOR
-
- Provisional force measuremnents on AMOR have shown that
- the operation of MA7 on AMOR is allowed with a field perpendicular
- to the beam at least up to 4 Tesla (estimation: 5 Tesla).
- The distance to the shielding wall between AMOR and SANS-II has
- to be at least 540 mm, measured from the aluminium window
- (or about 870 mm to the magnet centre).
-
- ''Torque Calculations''
-
- In general, the forces are not only radial, but also tangential,
- inducing a torque onto the magnet. For estimating the forces
- on the fixation, we need to take into account the distance of
- the fixation points from the coil center.
-
- For MA7, with a mean coil radius of about 100 m and fixation points
- at about 150 mm for the coil center, we get the following:
-
- Ro: object distance (mm)\\
- phi: angle (deg) between field direction and direction of object, for maximum force on fixation\\
- Fp: force when object on magnet axis (in field direction)
- Ft: maximum total force on fixation
-
- ||Ro ||phi ||Ft / Fp
- |<600 | 0 | 1.0
- | 800 | 20 | 1.04
- | 1000 | 27 | 1.13
- | 1200 | 32 | 1.25
-
- For the distance to the shielding wall we have to add 1/5 of the edge
- distance for the mean distance of the material that has to be taken
- into account (870 * 6/5 = 1044 mm).
-
- Measured force at 3.4 Tesla: 180 N.
- Extrapolated to 5 Tesla: 390 N.
- Factor 1.2 for including torque: 470 N.
+ [MA7/asysym.jpg]
+ !Asymetric mode
+
+ For changing from symmetric mode to asymmetric mode and vice versa:
+
+ * on the top of the magnet under the aluminium cyclinder:
+ ** make sure that the magnetic field is zero (IPS: shown current is 0 AND "persistent mode" LED is off)
+ ** switch the magnet power supply IPS off
+ ** open the cap using the screws marked on the picture above
+ ** switch the cable from the SYM pin to ASY pin (or vice versa)
+ ** the cable connected to the COM pin must always stay connected
+ ** close the cap
+ ** switch the magnet power supply on
+ * change the configuration of the IPS:
+ ** press RAISE+LOWER+LOC/REM simultanously ("tESt" and "t 00" appears)
+ ** press LOWER to go to "t 07", and then LOC/REM (""SUP" and "S 00" appears)
+ ** press LOWER 5 times to go to "S 11" and then press LOC/REM (the induction value appears)
+ ** press and hold LOC/REM and change the value with RAISE or LOWER, release LOC/REM when done
+ ** press RAISE 7 times to go to "S 02" and then press LOC/REM (the value for max. current appears)
+ ** press and hold LOC/REM and change the value with RAISE or LOWER, release LOC/REM when done
+ ** press LOWER once to go to "S 01" and then press LOC/REM (the value for max. current appears)
+ ** press LOC/REM again (the value for max. field appears)
+ ** press and hold LOC/REM and change the value with RAISE or LOWER, release LOC/REM when done
+ ** press LOWER once to go to "S 00" and then press LOC/REM ("tESt" and "t 00" appears)
+ ** press LOC/REM again ("Stor.y" appears) and again
+
+ ||Parameter || Value for Sym || Value for Asym
+ |S11 (coil inductance) | 112 | 78.7
+ |S02 (max. current) | 96.636 | 100.657
+ |S01 (max. field: second value)| 6.8 | 6.2
+

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