DR dipole (15 deg)

A new 15 deg bend magnet was designed to operate at higher beam energy and to minimize higher order multipoles.

Magnet Design

Jay's magnet design model

• TN JLab-TN-19-041 media:19-041.pdf
• Canting coils +/- 0.8 deg is predicted to achieve equal focusing in both planes

ME drawings which were used by Milhous to fabricate the coil (square wire, Feb 11, 2020)

We went through both square and round wire designs; finally used a round wire

• Dipole fixture media:200KeVYDipoleFixture-JL0087295.pdf
• Dipole winding media:200KeVYDipoleCoil-JL0087835.pdf

Intermediate drawings and mark-ups

• Oct 18, 2019 - Final 15 deg coil fixture => Drawing media:191018_15_COIL_FIXTURE.pdf
• Oct 23, 2019 - Jay mark-up for low- and high- energy coil => Drawing media:191023_Jay_dwg_markup.pdf, Specification media:191023_Jay_spec.docx

Magnet Shims for canted operation

• media:MDR_shim.pdf
• Laminate shim stock (2 mil/layer * 31 layers = 64 mil laminate, where each 2 mil layer can be peeled away)
• 28 mil shim needed for 1.688 deg angle between upper and lower coils (top 0.844 deg cw, bottom 0.844 deg ccw)
• each 2 mil layer of shim corresponds to a change in this angle by 0.048 deg (e.g. 28=>30 mil reduces angle to 1.640 deg, or 28=>26 mil increases angle 1.736 deg)
• we have 6 shims on hand, that is, we may choose up to 6 angles

Fabrication

Milhous was awarded fabrication of two DR magnets (four halves).

• Oct 5, 2020 (M. Beck) First half received from Milhous last week. The dimension inspection of the aluminum coil fixture is correct. Electrical testing, hipot and surge testing at 500V is completed, all meet JLAB acceptance criteria. Can not confirm turn count is correct with this kind of winding process and there is no additional coil to conduct coil comparison testing. It might be reasonable to assume the wire count is correct as we only have one halve section and no mapping can occur until we receive the next halve. Coil appearance looks reasonable for the fashion used for fabrication/winding. We just need 3 more halve sections to put these magnets together, after QA is completed on the additional 3 articles we will begin mapping. Milhous winding another half, will shop to JLab ASAP, within a week or so

Measurments

• MMF measurements of DR001 - media:Dipole_15deg_DR001_FieldMap.txt
• MMF measurements of DR002 (installed at CEBAF) - media:Dipole_15deg_DR002_FieldMap.txt

(January 13 2021 - MMF coil measurements)

Magnet DR01

TOP-SN#01 L/60Hz=1.617mH DCR=915.9 milliohm BOTTOM-SN#02 L/60Hz=1.563mH DCR=887.1 milliohm

Magnet DR02

TOP-SN#03 L/60Hz=1.527mH DCR=881.5 milliohm BOTTOM-SN#04 L/60Hz=1.540mH DCR=887.3 milliohm

From Jay - The ratio of inductances suggests a 1.7% turns discrepancy while resistance suggests 3.2% top vs bottom in DR01. (inductance goes as N^2, resistance as N). I suggest using the DR02 in the machine.

DR Magnet Analysis

• Riad's analysis of the two dipoles - media:Dipole15deg_FieldMap.pptx