Locating the magnetic center of the SSC CDM using a temporary quadrupole field

Abstract

The SSC dipole magnets must be very accura_ly the extreme purity of the magnetic field and the fact that the aligned for the accelerator to work correcdy. To align the moles have an averagecoil radius of 12 mm while the magnet magnets one must accurately know the center of the magnetic bore radius is 25 mm. field. However, locating the center is difficult because of the extremeuniformityof thedipolefield. A technique hasbeen Analternate technique hasbeendeveloped whichallowsthe developed to determine the magnetic centerof the SSCdipole useof directmagneticcentering whileavoidingthe problems magnetunder ambient test conditions. This technique associated with usingfceddown on a dipole magnet. This involves flowing currentin the upperhalf of the coilsin the techniqueinvolvesflowing currentin the upperhalf of the directionoppositeto the currentin the lower half. This is coilsin thedirectionopposite to thecurrentin the lowerhalf. doneusinga temporary leadconnected to the splice joiningthe The resultingfield is predominandyskew quadrupole,as two coil halves and two matchedpower supplies. The shownin Figure 1,andhashighfield gradientswhichallow resultingfield isprimarilyskewquadrupole andhashighfield thecenterto beaccm'awly locatedusinga moleandfeeddown gradients whichallow thecentertobeaccurately located.The analysis,lt shouldbe notedthat thisis nota truequadrupole, viability of this methodhasbeen verified by analysisusing sincesymmetryabout45°and135°axesis notsatisfied,and Taylor seriesexpansionof the resulting magnetic field, substantial amountsof higherordertermsarepresent.We Analysis hasalsoverified that off-the-shelfpowersupplies shall,however, referto thistechnique asthe "skewquadrupole havelowenough mismatchto be usedin thistechnique.The centering technique". analytacal resultshave been verified through the test of a short dipole magnet at the Brookhaven National Laboratory.Reversing the current direction in the lower half of the magnet is done using a temporary lead connected to the splice

Quench performance and field quality of DX dipoles for RHIC

“…Any radial offset of the measuring coil axis with respect to the magnetic axis is a source of error in the For all the other types of dipoles in RHIC, the Quadrupole Configured Dipole (QCD) method [3] was used for data centering. This method requires a separate measurement with the two magnet coil halves powered with opposite currents.…”