The NHMFL has installed a 24.6 T (Γ1 GHz 1 H) resistive ture of 8ΠC and exits the magnet from the bottom with a temperature of around 35ΠC. Each current lead has current-magnet with improved homogeneity to explore possibilities for NMR spectroscopy at field strengths higher than those carrying capability according to MCM 3000 (equivalent to a copper rod 44 mm in diameter) and is jacketed by circulating obtained in current superconducting magnets. Here, a characterization of this magnet is presented along with a discus-water to prevent overheating. The current leads, water pipes, and magnet are placed under a platform that is utilized by sion of spectroscopic implications and the first-phase technical solutions. In addition, 2 H NMR spectra of powders and experimenters to gain top loading access to the magnet. The magnet rests on legs that position the bottom plate 920 mm oriented samples demonstrate some advantages and disadvantages in working at very high magnetic fields.
from the ground, ensuring access to the bore from below. The magnet center is 587 mm from the top flange, and the Currently, the highest magnetic fields available in superconducting magnets are less than 21 T ( 900 MHz for experimentally available bore is 32.0 mm in diameter. The bore tube is circumscribed by the water-cooled stacks of 1 H ) . Resistive magnets offer higher field strengths at the expense of temporal stability and field homogeneity. In perforated copper plates or Bitter disks, which are connected in series. To increase the homogenous volume and to im-this paper, we present these temporal and spatial homogeneity problems that are associated with the 24.6 T resistive prove the Z-axis spatial homogeneity of this magnet, a 52 mm section at the center of coil B (Fig. 1) was electrically magnet installed at the NHMFL ( 1 ) and present the first phase corrections that permit moderate-resolution solid-shorted (1).
The power supply and cooling-water temperature influ-state NMR spectroscopy.
Literature abounds (2-5) on the advantages and disad-ence the temporal stability of the magnet. A 1ΠC increase in the inlet water temperature causes a 17 ppm decrease in the vantages of high magnetic fields for NMR spectroscopy. The advantages include enhanced sensitivity and resolution, magnetic field strength due to a change in magnet efficiency.
The power supply has a noise level of 10 ppm manifested reduction in second-order effects such as those between Zeeman and quadrupole interactions, changes in the relaxation as 60 Hz noise and its harmonics, plus some high-frequency noise, e.g., 1440 Hz, presumed to be rectifier switching properties, and increased chemical-shift dispersion, among others. In the 24.6 T magnet system, two advantages of high noise. Under normal operating conditions, the inlet water temperature varies by less than 0.4ΠC if no other magnet is B 0 fields are demonstrated for solid-state 2 H spectra: (1) reduction of tau values in quadrupole echo sequences that ramping. The total temporal instability under these conditions is on the order of 16 ppm as shown in Fig. 2A. In the allows for the detection of spin sites possessing short relaxation times and (2) enhanced sensitivity.
same figure, a strong correlation between the inlet water temperature and the 2 H resonance frequency (D 2 O in a 2 mm Figure 1 shows a cross section of the magnet, which consists of three concentric stacks of Bitter disks of height 470 sphere) is demonstrated. The temporal fluctuations display a 2 min oscillatory behavior, which mimics the water tempera-mm and diameter 610 mm, contained in a stainless steel housing. The magnet is located in a bay that affords two 10 ture control feedback system when operating in auto mode.
Placing the water temperature control system in manual MW power supplies and a cooling water loop. There are two current leads attached to the magnet, providing a maxi-mode greatly diminishes this periodicity (data not shown).
To compensate for the temporal instability, a field/fre-mum total of 40 kA. This particular magnet consumes, at full field, 12.6 MW at 35.5 kA. Under these conditions, quency lock unit and a flux stabilizer have been installed.
The former corrects for low-frequency drift (Γ΅5 Hz) caused deionized cooling water is cycled through the magnet at the rate of 4500 L/min at a pressure of 2 MPa (300 psi). Cooling by cooling water and other factors, while the latter corrects for high-frequency fluctuations caused by the power supply water enters the magnet from the top with an inlet tempera-212