16
R. Rüffer and A. I. Chumakov
and synchrotron radiation based science, respectively, will never result in optimum
conditions for both communities. Therefore, already shortly after first SR experiments in the 70th, discussions started e.g. in Europe for a dedicated high-energy SR
source. This was as well an endeavour, which should finally last for more than a
decade. The Mössbauer project was one of the very well adapted cases for such a
high-energy source especially due to the high transition energies of nuclear levels.
It really neededd a vision and courage to make the case for those early proposals of
an European SR facility [29] without having seen any “resonant quanta”! However,
it was important and essential and was rewarded with a first dedicated high-energy
SR facility in the world, the ESRF, and a Mössbauer beamline, called later Nuclear
Resonance beamline.
During the discussion of that facility and also later during the start-up and continuous operation a strong community was mandatory for a successful and promising
future. This is nowadays even more important with all the frequent evaluations,
comparisions between projects, and short term goals. Without such a community,
the proper networking, and the endless fights even the best ideas are damned to
fail. So far the nuclear resonance community is small and has to make up in the
synchrotron radiation scene.
1.2.4 First Results—The Needle in the Haystack
In the course to find the needle in the haystack nearly every avenue described above,
and may be more, has been tried over nearly a decade of unsuccessful attempts.
However, only very few of those attempts have been reported and may be traced
back [50].
Eventually, the pure nuclear reflection strategy brought the break-through in a
more than expected and convincing clearness [8].
The measurements were conducted at the Mössbauer test station at HASYLAB
located at the storage ring DORIS (Desy, Hamburg). DORIS was running in 2and 4-bunch mode with 480 ns and 240 ns spacing, respectively, and provided SR
from a bending magnet. The original experimental set-up is shown in Fig. 1.3. 22 m
downstream of the source point the high-heat-load monochromator, two Ge (111)
single crystals, monochromatized the SR at 14.4 keV with ΔE = 13 eV. After the
monochromator a beam size of 2 mm × 20 mm (v × h) was defined by a slit system and
an intensity of about 10
9 photons/(mA s) measured. Eventually, (3–6)×10
10 14.4 keV
photons/s were available for the experiment.
The nuclear monochromator consisted of two 15-μm thick single-crystalline films
of YIG (88% enriched in
57 Fe) epitaxially grown on the [100] surface of a gadolinium
gallium garnet (GGG) single crystal with 30 mm in diameter. An amount of about 10 g
57 Fe, purchased over several years, and several years of discussion were necessary
for the conviction and production of those films by the Philips research laboratory in
Hamburg. The two crystals were aligned in non-dispersive, and with respect to the
high-heat-load monochromator, in dispersive geometry. Both YIG crystals were set
R. Rüffer and A. I. Chumakov
and synchrotron radiation based science, respectively, will never result in optimum
conditions for both communities. Therefore, already shortly after first SR experiments in the 70th, discussions started e.g. in Europe for a dedicated high-energy SR
source. This was as well an endeavour, which should finally last for more than a
decade. The Mössbauer project was one of the very well adapted cases for such a
high-energy source especially due to the high transition energies of nuclear levels.
It really neededd a vision and courage to make the case for those early proposals of
an European SR facility [29] without having seen any “resonant quanta”! However,
it was important and essential and was rewarded with a first dedicated high-energy
SR facility in the world, the ESRF, and a Mössbauer beamline, called later Nuclear
Resonance beamline.
During the discussion of that facility and also later during the start-up and continuous operation a strong community was mandatory for a successful and promising
future. This is nowadays even more important with all the frequent evaluations,
comparisions between projects, and short term goals. Without such a community,
the proper networking, and the endless fights even the best ideas are damned to
fail. So far the nuclear resonance community is small and has to make up in the
synchrotron radiation scene.
1.2.4 First Results—The Needle in the Haystack
In the course to find the needle in the haystack nearly every avenue described above,
and may be more, has been tried over nearly a decade of unsuccessful attempts.
However, only very few of those attempts have been reported and may be traced
back [50].
Eventually, the pure nuclear reflection strategy brought the break-through in a
more than expected and convincing clearness [8].
The measurements were conducted at the Mössbauer test station at HASYLAB
located at the storage ring DORIS (Desy, Hamburg). DORIS was running in 2and 4-bunch mode with 480 ns and 240 ns spacing, respectively, and provided SR
from a bending magnet. The original experimental set-up is shown in Fig. 1.3. 22 m
downstream of the source point the high-heat-load monochromator, two Ge (111)
single crystals, monochromatized the SR at 14.4 keV with ΔE = 13 eV. After the
monochromator a beam size of 2 mm × 20 mm (v × h) was defined by a slit system and
an intensity of about 10
9 photons/(mA s) measured. Eventually, (3–6)×10
10 14.4 keV
photons/s were available for the experiment.
The nuclear monochromator consisted of two 15-μm thick single-crystalline films
of YIG (88% enriched in
57 Fe) epitaxially grown on the [100] surface of a gadolinium
gallium garnet (GGG) single crystal with 30 mm in diameter. An amount of about 10 g
57 Fe, purchased over several years, and several years of discussion were necessary
for the conviction and production of those films by the Philips research laboratory in
Hamburg. The two crystals were aligned in non-dispersive, and with respect to the
high-heat-load monochromator, in dispersive geometry. Both YIG crystals were set