A magnet apparatus comprising: a first vacuum chamber; a second vacuum chamber; a first magnet disposed within the first vacuum chamber such that the first magnet can be thermally isolated from the exterior of the first vacuum chamber; at least one load connector (22, 26, 1122) extending from the first vacuum chamber into the second vacuum chamber so that a load on the first magnet can be transferred to the second vacuum chamber, wherein the load connector (22, 26, 1122) is in thermal contact with the first magnet and can be thermally isolated from the exterior of the first vacuum chamber and the exterior of the second vacuum chamber, wherein the first vacuum chamber comprises a first sealing arrangement (24,1124) through which the load connector (22, 26, 1122) extends and the second vacuum chamber comprises a second sealing arrangement (24,1124) through which the load connector (22, 26, 1122) extends, and wherein a third vacuum chamber (46, 1146) through which the load connector extends and which is disposed between the first vacuum chamber and the second vacuum chamber is formed between the first and second sealing arrangements (24,1124, 28, 1128) and sealed from the first and second vacuum chambers by the first and second sealing arrangements, wherein the first sealing arrangement (24, 1124) comprises a flexible thermally insulating coupling (36, 1136) provided between the load connector (22, 26, 1122) and an inner wall of the first vacuum chamber, and the second sealing arrangement (24,1124) comprises a flexible thermally insulating coupling provided between the load connector and an inner wall of the second vacuum chamber. a first vacuum chamber; a second vacuum chamber; a first magnet disposed within the first vacuum chamber such that the first magnet can be thermally isolated from the exterior of the first vacuum chamber; at least one load connector (22, 26, 1122) extending from the first vacuum chamber into the second vacuum chamber so that a load on the first magnet can be transferred to the second vacuum chamber, wherein the load connector (22, 26, 1122) is in thermal contact with the first magnet and can be thermally isolated from the exterior of the first vacuum chamber and the exterior of the second vacuum chamber, wherein the first vacuum chamber comprises a first sealing arrangement (24,1124) through which the load connector (22, 26, 1122) extends and the second vacuum chamber comprises a second sealing arrangement (24,1124) through which the load connector (22, 26, 1122) extends, and wherein a third vacuum chamber (46, 1146) through which the load connector extends and which is disposed between the first vacuum chamber and the second vacuum chamber is formed between the first and second sealing arrangements (24,1124, 28, 1128) and sealed from the first and second vacuum chambers by the first and second sealing arrangements, wherein the first sealing arrangement (24, 1124) comprises a flexible thermally insulating coupling (36, 1136) provided between the load connector (22, 26, 1122) and an inner wall of the first vacuum chamber, and the second sealing arrangement (24,1124) comprises a flexible thermally insulating coupling provided between the load connector and an inner wall of the second vacuum chamber.