A Method for Greatly Reduced Edge Effects and Crosstalk in CCT Magnets

Iron-free CCT magnet design offers many advantages, one being the excellent field quality and the absence of multipole components. However, edge effects are present, although they tend to integrate out over the length of the magnet. Many modern accelerator applications, however, require that these magnets are placed in an area of rapidly varying optics parameters, so magnets with greatly reduced edge effects have an advantage. We have designed such a magnet (a quadrupole) by adding multipole components of the opposite sign to the edge distortions of the magnet. A possible application could be the final focus magnets of the FCC-ee, where beam sizes at the entry and exit point of the magnets vary by large factors. We have then used this technique to effectively eliminate cross talk between adjacent final focus quadrupoles for the incoming and outgoing beams.Comment: Poster presented at MT25,25th International Conference on Magnet Technology, Amsterdam, August 27 - September 1, 201

Validation of a strand-level CICC-joint coupling loss model

Calculating the coupling losses in cable-in-conduit conductor (CICC) joints requires a large amount of numerical effort, which is why the numerical system is often reduced by grouping strands together. However, to better understand the loss behaviour, and eventually the stability mechanism in such joints, a full-sized model working on the level of individual strands is more desirable. For this reason, the numerical cable model JackPot-AC has been expanded to also simulate the coupling losses in a CICC joint. This model has been verified with AC loss measurements on a mock-up joint, which was subjected to an applied harmonic field at different angles. The mock-up joint consisted of two sub-sized CICCs connected by a copper sole. For additional verification the AC loss of one of these conductors and the copper sole was also measured separately. The results of the simulation agree with the measurements, and the model therefore proves to be a useful analytical tool for examining the coupling loss in CICC joint

Incidence of intraoperative nausea and vomiting during spinal anaesthesia for Caesarean section in two Cape Town state hospitals

Background: Intraoperative nausea and vomiting (IONV) during spinal anaesthesia (SA) for Caesarean section (CS) is unpleasant and may interfere with surgery. The incidence of IONV during elective CS was studied, as well as the influence of ethnicity on this outcome.Methods: A total of 258 healthy term patients undergoing SA for elective CS were recruited to this prospective observational study conducted at two Cape Town Level 2 hospitals. Standard practice was employed for SA for CS at the University of Cape Town: 2 ml hyperbaric bupivacaine plus 10 μg fentanyl at the L3/4 interspace, and 15 mL/kg crystalloid coload. Spinal hypotension was managed with phenylephrine boluses according to a standard protocol. Nausea and/or vomiting were treated by restoration of blood pressure, and metoclopramide. Intraoperative complaints of nausea, and vomiting, were noted. Patients were also interviewed postoperatively as to any experience of intraoperative or previous history of nausea.Results: Of the 258 patients enrolled in the audit, 112 (43.4%) were non-African and 146 (56.6%) were Black African patients. The overall incidence (95% CI) of nausea was 0.32 (0.27–0.38), with 20% occurring prior to and 11% after the delivery. The overall incidence of vomiting was 0.07 (0.05–0.11), with 3.2% occurring prior to and 3.8% after delivery. The incidence of nausea and/or vomiting was 0.33 (0.28 – 0.40). Black Africans experienced significantly less nausea than non-African patients (36/145 [24.8%] vs. 47/112 [42.0%] respectively, p = 0.004). There was no significant difference in the incidence of vomiting (10/145 [6.8%] vs. 8/112 [7.1%] respectively). The odds of experiencing intraoperative nausea for patients with any blood pressure value < 70% of baseline were 2.46 (95% CI 1.40–4.33).Conclusions: Though in keeping with international standards, the clinically significant incidence of nausea and/or vomiting of 33% requires adjustments to the management protocol for spinal hypotension. The inclusion of ethnicity as a risk factor for nausea during SA for CS should be considered.Keywords: Caesarean section, ethnicity, intraoperative, nausea and vomiting, spinal anaesthesi

The FCC-ee Interaction Region Magnet Design

The design of the region close to the interaction point of the FCC-ee experiments is especially challenging. The beams collide at an angle (+-15 mrad) in the high-field region of the detector solenoid. Moreover, the very low vertical beta_y* of the machine necessitates that the final focusing quadrupoles have a distance from the IP (L*) of around 2 m and therefore are inside the main detector solenoid. The beams should be screened from the effect of the detector magnetic field, and the emittance blow-up due to vertical dispersion in the interaction region should be minimized, while leaving enough space for detector components. Crosstalk between the two final focus quadrupoles, only about 6 cm apart at the tip, should also be minimized.Comment: Poster presented at IPAC16, May 8-13, Busan, Kore

Mechanical Effects of the Nonuniform Current Distribution on HTS Coils for Accelerators Wound With REBCO Roebel Cable

Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 WP10 Future Magnets collaboration is aiming at testing HTS-based Roebel cables in an accelerator magnet. The demonstrator should produce around 17 T, when inserted into the 100-mm aperture of Feather-M2 13-T outsert magnet. HTS Roebel cables are assembled from meander-shaped REBCO-coated conductor tapes. In comparison with fair level of uniformity of current distribution in cables made out of round Nb-Ti or Nb3Sn strands, current distribution within the coils wound from Roebel cables is highly nonhomogeneous. It results in nonuniform electromagnetic force distribution over the cable that could damage the very thin REBCO superconducting layer. This paper focuses on the numerical models to describe the effect of the nonhomogeneous current distribution on stress distribution in the demonstrator magnet designed for the EuCARD-2 project. Preliminary results indicate that the impregnation bonding between the cable glass fiber insulation and layer-to-layer insulation plays a significant role in the pressure distribution at the cable edges. The stress levels are safe for Roebel cables. Assuming fully bonded connection at the interface, the stresses around the edges are reduced by a large factor