Heinrich B Stuhrmann

With the inauguration of the small-angle instrument D11 of the Institute Laue–Langevin (ILL) in September 1972 neutron scattering revolutionized methods of contrast variation. Very soon D11 was oversubscribed by proposals relying on isotopic substitution of hydrogen isotopes. At the same time in Oxford first experiments of polarised neutron diffrac...

A differentiation between dynamic polarised protons close to tyrosyl radical sites in catalase and those of the bulk is achieved by time-resolved polarised neutron scattering. Three radical sites, all of them being close to the molecular centre and the heme, appear to be equally possible. Among these is tyr-369 the radial site of which had previous...

A tyrosyl radical, as part of the amino acid chain of bovine liver catalase, supports dynamic proton spin polarization (DNP). Finding the position of the tyrosyl radical within the macromolecule relies on the accumulation of proton polarization close to it, which is readily observed by polarized neutron scattering. The nuclear scattering amplitude...

An unexpected and not always easily discernible feature in the picture of magnetic neutron scattering is widening the outlook on micromagnetic architecture [Mettus & Michels (2015). J. Appl. Cryst.48, 1437–1450].

Motivated by potentially important applications in structural biology, experiments of time-resolved polarised neutron scattering from dynamic polarised proton spin targets were undertaken in order to elucidate the build-up of proton spin polarisation near paramagnetic centres. Organic radicals of different size like EHBA-Cr-V, DPPH and a biradical...

Der native Zustand der Myoglobinmoleküle in wäßriger Lösung ohne Salzzusatz bleibt zwischen pH 7 und pH 4,6 unverändert. Durch HCl-Zugabe erfolgt bei pH 4,6 bis 4,1 eine schwache Assoziation ohne eigentliche Konformationsänderung. Das mittlere Mol.-Gew. steigt bis auf das 1,5-fache des ursprünglichen Wertes. Diese Assoziation erreicht bei pH 4,1 ei...

The mathematical formalism of contrast variation is presented in terms of an expansion of spherical harmonics. Early attempts of contrast variation in X-ray small-angle scattering are compared with the corresponding more versatile techniques of neutron small-angle scattering. Some applications in life sciences illustrate the power of nuclear spin c...

The experiments of time-resolved polarized neutron scattering from dynamically polarized nuclei of the EHBA-Cr(V) complex are reviewed. The analysis of the data is extended to protiated samples, and the existence of polarized proton spin domains in the absence of deuteration is shown. It is concluded that pulsed neutron sources may gain considerabl...

Crystal diffraction of three membrane proteins (cytochrome bc1 complex, sarcoplasmic reticulum Ca²⁺ ATPase, ADP-ATP carrier) and of one nucleoprotein complex (leucyl tRNA synthetase bound to tRNAleu, leuRS:tRNAleu) was tested at wavelengths near the X-ray K-absorption edge of phosphorus using a new set-up for soft X-ray diffraction at the beamline...

Methods of contrast variation are tools that are essential in macromolecular structure research. Anomalous dispersion of X-ray diffraction is widely used in protein crystallography. Recent attempts to extend this method to native resonant labels like sulfur and phosphorus are promising. Substitution of hydrogen isotopes is central to biological app...

Dynamic nuclear spin polarization (DNP) is mediated by the dipolar interaction of paramagnetic centres with nuclear spins. This process is most likely to occur near paramagnetic centres at an angle close to 45° with respect to the direction of the external magnetic field. The resulting distribution of polarized nuclear spins leads to an anisotropy...

Applications of X-ray absorption spectroscopy in two areas of liquid state studies using synchrotron radiation are reviewed. One area concerns with the determination of the local structure, bonding and dynamics at the metal site of transition metal complexes using Extended X-Ray Absorption Fine Structures (EXAFS) and X-Ray Absorption Near Edge Stru...

In this short review of recent advances in XANES we have discussed the use of this spectroscopy to probe the geometry of local structure via multiple scattering effects in the real space and and the local partial unoccupied density of states in metals via the band structure approach. Several important aspects of x-ray absorption spectroscopy have n...

The use of anomalous X-ray scattering of light elements like sulfur and phosphorus is of particular interest in biological structure research. These elements serve as native labels in proteins, nucleic acids and membranes. Their medium scattering power is drastically changed at their K absorption edges at wavelengths between 5 and 6 Å where X-ray a...

The first observations of an increase of the reactivity between gases in the presence of a metal were made, almost one hundred years ago, by chemists like Davy or Thenard. This pioneer work led Berzelius and Mitscherlich to define the concept of “decomposition of species by contact under a catalytic force”. Since then much work has been done in ord...

The strengths and weaknesses of EXAFS in determining the radial distribution of the first nearest neighbours in coordination compounds are well known. We point out here how local information given by EXAFS upon the first coordination sphere can be used to characterize short or long range order or disorder in low dimensional materials. Low tempera...

This paper aims at showing the interest of synchrotron radiation for various applications in the field of Inorganic Chemistry. After a short survey of the main properties of this light source and some characteristics of the storage rings, two main applications are reviewed. The first one concerns X-ray scattering techniques. The study of very tiny...

Current views on the structure and function of biological membranes imply a great variety of dynamical aspects. These range from the dynamic phase behaviour of phospholipids and conformational variations of membrane proteins during membrane-associated processes, to the interactions between membranes in fusion and pore formation. The structural desc...

Small angle X-ray scattering and diffraction methods can provide information about chromatin structure at the levels of nucleosomes, chromatin fibre and whole nuclei. Making use of the high flux and point focusing achieved on synchrotron radiation cameras it has been possible to carry out systematic static and kinetic investigations of chromatin st...

Low-resolution small-angle neutron scattering measurements can benefit from polarized protons to generate scattering contrast profiles. In a recently developed technique, time-resolved polarized SANS tries to make use of spatial polarization gradients created around paramagnetic centres at the onset of dynamic nuclear polarization. The time constan...

This contribution is meant to highlight some progress in those areas of contrast variation which are known to be technically more difficult but which promise interesting applications. These concern the use of the anomalous dispersion of light elements, like sulfur and phosphorus in structural studies and experiments of polarized neutron scattering...

Polarized neutron scattering from dynamically polarized nuclear spin targets has become a method of macromolecular structure research. As the cross-section of coherent neutron scattering of the hydrogen isotopes 1H and 2H differ strongly and even more in their dependence on nuclear polarization, methods of specific isotopic substitution are used fo...

We report on time-resolved small-angle polarised neutron scattering from domains of polarised protons created by dynamic nuclear polarisation in frozen deuterated glycerol water solutions containing a small amount of paramagnetic centres. In order to observe the rapid build-up of the polarisation of the protons around the paramagnetic ions and to s...

We have investigated the process of dynamic proton polarisation by means of time-resolved polarised small-angle neutron scattering (SANS) on frozen solutions of EHBA-CrV molecules in glycerol-water mixtures as a function of the concentration of EHBA-CrV and for different degrees of deuteration of the solvent. In the EHBA-CrV complex, the spins of t...

Resonance (or anomalous) X-ray scattering of partially ordered macromolecular structures, amorphous materials and solutions is encountered in the near edge region of X-ray absorption edges where the resonant real part f' of atomic form factors shows the strongest dispersion. The requirements of spectral brilliance in the near absorption edges can o...

Phosphorus is an abundant element in living organisms. It is traceable by its X-ray absorption spectrum which shows a strong white line at its K-edge, comparable with that observed for the LIII edges of rare earth ions. With purple membrane, the variation of the imaginary part of the anomalous dispersion of phosphorus is found to be close to 20 ano...

The utilization and the potential of softer and soft X-rays in macromolecular crystallography as well as the challenges associated with the corresponding diffraction experiments and their possible remedies are reviewed.

We present a measurement of the longitudinal spin cross section asymmetry for deep-inelastic muon-nucleon interactions with two high transverse momentum hadrons in the final state. Two methods of event classification are used to increase the contribution of the photon-gluon fusion process to above 30%. The most effective one, based on a neural netw...

In the past 3 years a series of experiments have shed new light on the mechanism of dynamic nuclear polarisation (DNP). Time-resolved polarised small-angle neutron scattering and nuclear magnetic resonance have been used simultaneously to study the nuclear polarisation build-up around paramagnetic centres during DNP. This approach, which aims at vi...

The unique aspects of neutron scattering in biology rely largely on the extraordinary parameters of interaction of neutrons with hydrogen nuclei. The origin of isotopic and spin incoherent scattering and its possible implication for neutron diffraction from protein crystals are described. The impact of a change in the coherent scattering length of...

We present a measurement of the longitudinal spin cross section asymmetry for deep inelastic muon-nucleon interactions with two high transverse momentum hadrons in the final state. Two methods of event classification are used to increase the contribution of the Photon Gluon Fusion process to above 30%. The most effective one, based on a neural netw...

URL: http://www-spht.cea.fr/articles/S03/010

Soft X-ray diffraction from synchrotron radiation gives access to the use of MAD (multi-wavelength anomalous diffraction) and DAFS/DANES (diffraction anomalous fine structure/diffraction near edge structure) methods with relatively light elements down to Z=14 (silicon), including elements such as sulfur and phosphorus essential in life. It also exp...

Mapping of protein positions in the ribosomal subunits was first achieved for the 30S subunit by means of neutron scattering about 15 years ago. Since the 50S subunit is almost twice as large as the 30S subunit and consists of more proteins, it was difficult to apply classical contrast variation techniques for the localisation of the proteins. Pola...

The protein L2 is found in all ribosomes and is one of the best conserved proteins of this mega-dalton complex. The protein was localized within both the isolated 50 S subunit and the 70 S ribosome of the Escherichia coli bacteria with the neutron-scattering technique of spin-contrast variation. L2 is elongated, exposing one end of the protein to t...

Domains of polarized protons have been created around paramagnetic centers in alcohols by dynamic nuclear polarization (DNP) methods, rf saturation and/or adiabatic fast passage polarization reversal. The decay of the polarization gradient has been indirectly observed by NMR methods. We aim at taking advantage of the possibility to create such clus...

Anomalous diffraction with soft X-ray synchrotron radiation opens new possibilities in protein crystallography and materials science. Low-Z elements like silicon, phosphorus, sulfur and chlorine become accessible as new labels in structural studies. Some of the heavy elements like uranium exhibit an unusually strong dispersion at their M(V) absorpt...

The feasibility and a review of progress in the long-wavelengths anomalous dispersion technique is given in the context of the development of beamline ID1 of the ESRF for such studies. First experiments on this beamline and their analyses are described. The first study reports on the use of uranium which exhibits an unusually strong anomalous dispe...

A muon beam polarimeter was built for the SMC experiment at the CERN SPS, for beam energies of 100 and 190 GeV. The beam polarisation is determined from the asymmetry in the elastic scattering off the polarised electrons of a ferromagnetic target whose magnetisation is periodically reversed. At muon energies of 100 and 190 GeV the measured polarisa...

A muon beam polarimeter was built for the SMC experiment at the CERN SPS, for beam energies of 100 and 190~GeV. The beam polarisation is determined from the asymmetry in the elastic scattering off the polarised electrons of a ferromagnetic target whose magnetisation is periodically reversed. At muon energies of 100 and 190~GeV the measured polarisa...

The polarized target of the Spin Muon Collaboration at CERN was used for deep inelastic muon scattering experiments during 1993 to 1996 with a polarized muon beam to investigate the spin structure of the nucleon. Most of the experiments were carried out with longitudinal target polarization and 190 GeV muons, and some were done with transverse pola...

Arrays of limited streamer tubes of the Iarocci type were deployed in our experiment at CERN as part of a forward muon detector system with provisions for the beam to pass through the center of each panel in the array. A total of 16 4 m×4 m panels were assembled with inductive readout strips on both sides of each panel. An active feedback system wa...

We present the results of the spin asymmetries A{sub 1} of the proton and the deuteron in the kinematic region extending down to x=6{times}10{sup {minus}5} and Q{sup 2}=0.01&hthinsp;GeV{sup 2}. The data were taken with a dedicated low {ital x} trigger, which required hadron detection in addition to the scattered muon, so as to reduce the background...

We present the results of the spin asymmetries Al of the proton and the deuteron in the kinematic region extending down to x = 6 x 10(-5) and Q(2) = 0.01 GeV2. The data were taken with a dedicated low x trigger, which required hadron detection in addition to the scattered muon, so as to reduce the background at low x. The results complement our pre...

The spin-dependent interaction of neutrons with nuclei is best exploited in experiments of polarised neutron diffraction from dynamic polarised nuclei. NMR methods like nuclear depolarisation or nuclear spin reversal by AFP act selectively on nuclei whose Larmor frequencies differ either because of their magnetic moments or their proximity to param...

Recent experiments carried out at the Anomalous Scattering Beam-line ID1 of ESRF are described which show that a cold helium atmosphere provides optimal conditions for protein crystallography with soft X-rays at wavelengths up to 6 Å. Image plates are suitable detectors for this wavelength range. The improvement with respect to earlier experiments...

Arrays of limited streamer tubes of the Iarocci type were deployed in our experiment at CERN as part of a forward muon detector system with provisions for the beam to pass through the center of each panel in the array. A total of sixteen 4 m x 4 m panels were assembled with inductive readout strips on both sides of each panel. An active feedback sy...

The 1996 data taking of the SMC experiment used polarized protons to measure the spin dependent structure function $g_1$ of the proton. Three liters of solid granular ammonia were irradiated at the Bonn electron linac in order to create the paramagnetic radicals which are needed for polarizing the protons. Proton polarizations of $\pm(90\pm2.5)\,\%...

We present a next-to-leading order QCD analysis of the presently available data on the spin structure function $g_1$ including the final data from the Spin Muon Collaboration (SMC). We present resu lts for the first moments of the proton, deuteron and neutron structure functions, and determine singlet and non-singlet parton distributions in two fac...

We present the final results of the spin asymmetries A1 and the spin structure functions g1 of the proton and the deuteron in the kinematic range 0.0008<x<0.7 and 0.2<Q2<100GeV2. For the determination of A1, in addition to the usual method which employs inclusive scattering events and includes a large radiative background at low x, we use a new met...

Besides EM and biochemical studies small angle scattering (SAS) examinations have contributed significantly to our current knowledge about the ribosomal structure. SAS does not only allow the validation of competing models but permits independent model building. However, the major contribution of SAS to ribosomal structure research derived from its...

Bacteriorhodopsin contains nine sulfur atoms from the nine methionine residues. The distribution of these sulfur atoms in the projected density map was determined from x-ray diffraction experiments using multiple wavelength anomalous diffraction (MAD) at the sulfur K-edge (5.02 A) with synchrotron radiation. The experiments were performed with unia...

The ribosome uses tRNAs to translate the genetic information into the amino acid sequence of proteins. The mass ratio of a tRNA to the ribosome is in the order of 1:100; because of this unfavorable value it was not possible until now to determine the location of tRNAs within the ribosome by neutron-scattering techniques. However, the new technique...

Ribosome research has reached an exciting state, where two lines of experimental research have considerably improved our understanding of the ribosomal functions. On one hand, functional analysis has elucidated principles of both the decoding process and the tRNA movement on the ribosome during translocation. Experimental data leading to current co...

We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 0.003<x<0.7 and Q2>1 GeV2. Compared to our previous publication on this subject, with the new data the statistical errors have been reduced by nea...

Polarized neutron scattering from dynamically polarized nuclear spin targets has become a method of macromolecular structure research. The contrast created by substitution of the hydrogen isotope 1H by 2H is increased by almost a factor of three if polarized neutrons are scattered by polarized nuclear spins in the sample (spin contrast variation)....

We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range $0.003<x<0.7$ and $Q^2>$1~GeV$^2$. Compared to our previous publication on this subject, with the new data the statistical errors have been reduce...

We present the final results of the spin asymmetries $A_1$ and the spin structure functions $g_1$ of the proton and the deuteron in the kinematic range $0.0008<x<0.7$ and $0.2<Q^2<100$ GeV$^2$. For the determination of $A_1$, in addition to the usual method which employs inclusive scattering events and includes a large radiative background at low $...

The technique of soft X-ray diffraction available at the beamline A1 of HASYLAB has been developed to a level which allows protein crystallography using sulfur and phosphorus as resonant native labels at wavelengths near the K-absorption edges. This has been achieved by increasing the transparency of the X-ray beam path and progress in the design o...

Isotopic substitution methods are widely used in neutron scattering for the determination of the in situ structure of macromolecular components in quaternary structures. The contrast created by the substitution of the hydrogen isotope 1H (proton) by 2H (deuteron) is the most prominent example. A further increase of contrast by a factor of three is...

We have measured the spin-dependent structure function $g_1^{\rm p}$ in inclusive deep-inelastic scattering of polarized muons off polarized protons, in the kinematic range $0.003 < x < 0.7$ and $1\gevtwo < Q^2 < 60\gevtwo$. A next-to-leading order QCD analysis is used to evolve the measured $\gpone(x,Q^2)$ to a fixed $Q^2_0$. The first moment of $...

We present a new measurement of the virtual photon proton asymmetry $A_1^{\rm p}$ from deep inelastic scattering of polarized muons on polarized protons in the kinematic range $0.0008 < x < 0.7$ and $0.2 < Q^{2} < 100$ GeV$^{2}$. With this, the statistical uncertainty of our measurement has improved by a factor of $2$ compared to our previous measu...

An analytic model of the deuteron absorption function has been developed and is compared to experimental NMR signals of deuterated butanol obtained at the SMC experiment in order to determine the deuteron polarization. The absorption function model includes dipolar broadening and a frequency-dependent treatment of the intensity factors. The high-pr...

Polarized neutron scattering from dynamically polarized targets has been used for the study of hydrogenous materials in several laboratories. A new variant, which is less dependent on specific deuteration, is proposed. This is based on the observation that a radio frequency (RF) field swept over a selected part of an NMR line depo-larizes the spins...

Practical aspects of low-resolution shape determination in small-angle scattering studies of biological macromolecules in solution are considered. The shape restoration method using spherical harmonics [Svergun, Volkov, Kozin & Stuhrmann (1996). Acta Cryst. A52, 419–426] is extended to account for deviations from the idealized model and to work dir...

Anomalous dispersion of X-ray diffraction at wavelengths near the X-ray K-absorption edge of sulfur at wavelengths around 5 A has been applied to single crystals of trypsin obtained from an ammonium sulfate solution. The multiwavelength anomalous-dispersion method based on 775 unique reflections (+183 Bijvoet mates) measured at three wavelengths ne...

Solutions of selectively deuterated 70 S Escherichia coli ribosomes and of free 30 S and 50 S subunits were studied by neutron scattering using contrast variation. The integrity of the partially deuterated particles was controlled by parallel X-ray measurements. Integral parameters of the entire ribosome, of its subunits and of the protein and rRNA...

Selectively deuterated 70 S E. coli ribosomes and isolated 30 S and 50 S subunits were analyzed by X-ray and neutron solution scattering. The resulting contrast variation data set (42 curves in total) was proven to be consistent in describing the ribosome as a four-phase system composed of the protein and rRNA moieties of both subunits. This data s...

The method of proton-spin contrast-variation was applied for determining the position of the messenger RNA within the elongating ribosome. Using an artificial mRNA fragment the mass center of the mRNA sequence covered by the ribosome could be localized for the pre- and the post-translocational elongation states. The mass center moves about 12 ± 5 Å...

The 70S ribosome from E.coli was analysed by neutron scattering focusing on the shape and the internal protein-RNA-distribution of the complex. Measurements on selectively deuterated 70S particles and free 30S and 50S subunits applying conventional contrast variation and proton-spin contrast-variation resulted in a total of 42 scattering curves. Pr...

Spin contrast variation as a method of polarized small angle neutron scattering (polarized SANS) by polarized nuclear spins (1H or 2D spins) was used in the last few years for the in situ structure research of the 70S ribosome of the E. coli bacteria. The increase of contrast obtained from polarization-dependent neutron scattering opened the possib...

Polarized neutron scattering from dynamic polarized targets is a new tool of macromolecular structure research. In frozen nuclear spin targets the polarization of isotopes can be eliminated selectively one by one till only a single isotope is left polarized. This technique has been applied successfully in biological structure research. It is extend...

By small-angle neutron scattering (SANS) we have analysed structural aspects of aquatic refractory organic substances (ROS) of different origin. Using GNOM, an indirect transform program for SANS data processing, size distribution functions were obtained from the scattering curves. Radii at the maxima of the distribution curves are found between 0....

Anomalous dispersion of X-ray diffraction from bovine trypsin has been measured at three wavelengths near the 1. Scaling of the experimental data and calculation of the anomalous difference Patterson map, showing the correlation between sulphur atoms. 2. Using the measured dispersion to calculate phases based on the known sulphur sites of the refin...

We present a new measurement of the spin-dependent structure function gd1 of the deuteron from deep inelastic scattering of 190 GeV polarized muons on polarized deuterons. The results are combined with our previous measurements of gd1. A perturbative QCD evolution in next-to-leading order is used to compute gd1(x) at a constant Q2. At Q2 = 10GeV2,...

A new technique for neutron scattering, the proton-spin contrast-variation, improves the signal-to-noise ratio more than one order of magnitude as compared to conventional techniques. The improved signal enables small RNA ligands within a large deuterated ribonucleic acid-protein complex to be measured. We used this technique to determine the posit...

We present a new measurement of the spin-dependent structure function $g_1^{\rm d}$ of the deuteron from deep inelastic scattering of $190~\mbox{GeV}$ polarized muons on polarized deuterons. The results are combined with our previous measurements of $g_1^{\rm d}$. A perturbative QCD evolution in next-to-leading order is used to compute $g_1^{\rm d}...

Biological applications of neutron scattering almost entirely rely on methods of isotropic substitution of hydrogen 1H by its heavier isotope 2H. The exchange of water by heavy water D2O has been most widely used for the characterization of the internal structure of complex particles, like viruses, mostly at low resolution. This method is known as...

Polarized neutron scattering is a probe of nuclear spin densities. It finds an important application in nuclear spin contrast variation. As an example the results from studies on ribosome bound tRNAs are presented. Selective nuclear spin polarization can be controlled by the rf bandwidth. The creation of spin label dependent polarization domains is...

Methods of isotopic substitution are widely used in neutron scattering for the determination of the in situ structure of macromolecular components. The contrast created by substitution of the hydrogen isotope 1H (proton) by 2H (deuteron) is the most prominent example in contrast variation. A further increase of the contrast is achieved if a polariz...

The problem of uniqueness of the low-resolution shape determination from small-angle scattering by isotropic monodisperse systems is considered. The particle shape is represented by the envelope function parameterized using spherical harmonics as described in a previous paper [Svergun & Stuhrmann (1991). Acta Cryst. A47, 736-744]. Computer simulati...

We report a large enhancement of 1.7 in deuteron polarization up to values of 0.6 due to frequency modulation of the polarizing microwaves in a two liters polarized target using the method of dynamic nuclear polarization. This target was used during a deep inelastic polarized muon-deuteron scattering experiment at CERN. Measurements of the electron...

We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering of polarised muons on polarised protons and deuterons in the range 0.003 < x < 0.7. From these asymmetries and the previously published inclusive spin asymmetries we determine, for the first time, the x-dependent...

Polarized neutron scattering from polarized nuclear spins in hydrogenous substances opens a new way of contrast variation. The enhanced contrast due to proton spin polarization was used for the in situ structure determination of tRNA of the functional complex of the E. coli ribosome.

We present a new measurement of the spin-dependent structure function g1d of the deuteron in deep inelastic scattering of 190 GeV polarised muons on polarised deuterons, in the kinematic range 0.003 < x < 0.7 and 1 GeV2 < Q2 < 60 GeV2. This structure function is found to be negative at small x. The first moment Γ1d=∫01g1ddx evaluated at Q02 = 10 Ge...

The wavelength region of soft X-ray diffraction has been extended to 6.8 Å which includes the K-absorption edge of silicon. From anomalous dispersion of small-angle scattering from a silicon triblock copolymer Si (styrene-butadiene-styrene)4 the distinct correlation function of silicon and the non-silicon atoms has been obtained. First X-ray diffra...

X-ray diffraction from a single crystal of the small ribosomal subunit of Thermus thermophilus was measured at five wavelengths near the K-absorption edge of phosphorus. The intensity of the low-order diffraction peaks varies strongly with the wavelength. It is influenced by the dispersion of contrast due to the P atoms of the ribosomal ribonucleic...

In cooperation with CERN, a dynamic polarized nuclear target station was built at GKSS-Research Center on SANS-1, aimed at investigation of biomolecule structure. The target consists of a 20 mmol/min dilution refrigerator, which has a basic temperature of 50 mK, a 2.5 T electromagnet, and a carcinotron which delivers the 4 mm microwave at a power u...