Cryomagnet system

Since the B-field must be parallel to the ion beam, the cryomagnet system requires a horizontal setup in contrast to that of NMR spectrometers. The magnetic fields of all... 

A layout of the nuclear resonance beamline ID18 of the European Synchrotron Radiation Facility in Grenoble, France. u27 and u20 stand for the revolver-type undulators with 27 mm period for one structure and 20 mm period for the other. OH1 and OH2 are the first and second optics hutches devoted to the accommodation of HHLM, slit systems (SI, S2), CRL, HRMs, and FM. EH1, EH2, and EH3 stand for the experimental hutches, while CC1-CC3 denote the control cabins. DIFF is the six-circle diffractometer, UHV the ultrahigh-vacuum system for ns/tu experiments, and CRYO the cryomagnet system. X-ray beam monitors and attenuators are not shown. 

Transmission Mossbauer spectrometer equipped by cryomagnetic system operating with an external magnetic field upto 10T and temperatures down to 1.5 K. 

As mentioned in the section of modes of operation for LC-NMR (Section 20.3.2), with the use of shielded cryomagnets, the location of the MS instrument will follow the same rule as for the HPLC. The most common modes of operation for LC-MS-NMR are on-flow and stop-flow. With stop-flow, the MS instrument can also be used to stop the flow on the chromatographic peak of interest that is to be analyzed by NMR. These two modes are presented here with an example. In the loop collection mode, the MS of the LC-MS-NMR system may also monitor the trapping of the chromatographic peak inside the loop. 

Working with an NMR spectrometer is slightly more difficult than, for instance, with an electron microprobe. As the NMR frequencies are all in the radio frequency range, NMR spectrometers are computer operated radio transmitting and receiving systems controlled by a computer. A receiver and transmitter antenna surrounds the sample, which is located in the cavity of a super-conducting cryomagnet. 

The complete vacuum unit can be baked out at 200°C in order to remove the remainder of the analytical samples introduced. An efficient water cooling system is necessary to have optimal temperature conditions for the turbomolecular pumps (90000 rpm) and the analyzer cell within the cryomagnet. 

The FT-ICR method described in Section 2.3.4 suffers only from one weak point It requires magnetic fields with intensities > (or =) 3 Tesla. Consequently, cryomagnets are required, with high costs either for acquirement or for maintenance. The commercial availability of mass spectrometers exhibiting high performances, but low initial cost, modest maintenance cost, and reduced size, is surely of great interest, and the Orbitrap system (Hu et al., 2005) is the answer to this need. 

Here, we show only a bare outline of the individual components in the overall system. This SYSTEM is capable of operation in inert atmosphere or vacuum. A melt/seed contact monitor is provided as well as a CCTV camera for observing and controlling the crystal diameter as it grows. Note that both the crucible and crystal rotation can be controlled. In order to control the heat-convection patterns which normally appear in the melt, an external cryomagnet is supplied. Its magnetic field controls heat losses, plus it maintains a better control of the crystal growth. A slave micro-processor controls both crystal diameter and meniscus-contact of the growing crystal. 

The experimental arrangement for the on-line coupling of a chromatographic separation system with an NMR cryomagnet is outlined in Figure 7-2. 

A new high temperature probehead has been constmcted for NMR measurements up to 900 K. The rf-coil made firom molybdenum wire of 0.5 mm diameter is fixed on a boron nitride cylinder which is located inside the furnace tube. The sample volume which is detected by the NMR coil is 10 mm in diameter and 15 mm in height. The furnace consists of a molybdenum wire resistance heater noninductively wound on an alumina tubing. A dc power supply has been used to avoid parasitic signals. The whole system is placed inside a water cooled vacuum recipient fitting into the cryomagnet. For recent reviews on high temperature NMR techniques see e.g. [11,12]. 

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