| 摘要 |
<p>A superconducting magnet comprises at least one superconducting winding 20 within an outer vacuum chamber (OVC) 10 with at least one thermal radiation shield 12 located between the said winding 20 and said chamber 10. A cooled surface or cryogen vessel 22 is provided and at least one refrigerator 26 is arranged to cool the cooled surface or cryogen vessel 22. The cooled surface or cryogen vessel 22 is arranged with an outer surface portion with a thermal emissivity at a liquid cryogen temperature which is greater than the average emissivity of the at least one superconducting winding 20 by at least 0.1. The said outer surface portion thermal emissivity may be provided by materials, treatment or coatings such as tarnished copper or stainless steel, brushed or sandblast or grit blast stainless steel, charcoal or cotton cloth, stainless steel wool, hard black anodised aluminium, black paint or carbon black. The said portion may be at least 20% or 30% or 50% with emissivity of 0.5 to 0.9. The surface may be corrugated and/or include thermally conductive fins. The refrigerator 26 is a recondensing refrigerator.</p> |
