大型放射光施設 SPring-8

問い合わせ番号

INS-0000000282

Electromagnet and closed-cycle helium refrigerator

  The normal conducting electromagnet is used for XMCD experiment. It generates a maximum magnetic field of 2 T at a 45 A feeding current with a set of poles placed 10 mm apart. Three sets of poles with different gaps are replaceable, and the available magnetic field changes correspondingly. The maximum field available with the use of each set of poles is shown in Table 1.
  The field polarity is reversed in 1.7 s by changing the polarity of the feeding current. The magnet is mountable on the Ω-circle of the diffractometer and is rotatable about the vertical axis. Additionally, the poles are rotatable in the vertical plane; field directions can be changed in parallel and perpendicular orientations, or at any desired angle with respect to the incident X-ray beam.
  The closed-cycle helium refrigerator or helium-flowing type cryostat is available for low-temperature measurements. The closed-cycle helium refrigerator can cool a sample to 20 K within 90 min, and the controllable temperature range spans between 20 and 300 K. The cold head is fit to the electromagnet. The refrigerator generates very little vibration. On the other hand, the helium-flowing type cryostat can cool a sample to 11 K within 30 min by using liquid helium. The controllable temperature range spans between 11 and 330 K. For both cryostats,  a number of sample holders are available; users can choose one appropriate for their experiment as well as for fitting to the gap between the poles.  The lowest temperatures available with the sample rods are shown in Table 1.

• Table 1. The maximum magnetic field and the lowest temperatures available from the use of a set of poles and a compatible sample holder

   

  Pole gaps (mm)	45	20	10
  Maximum magnetic field (T)	0.61	1.09	1.98
  Lowest temp. (Closed-cycle type) (K)	20	26	40
  Lowest temp. (He-flowing type) (K)	11	---	20

   

  

  Fig. 1. The electromagnet for XMCD measurements.