18 research outputs found
Coherent-Radiation Spectroscopy of Few-Femtosecond Electron Bunches Using a Middle-Infrared Prism Spectrometer
Modern, high-brightness electron beams such as those from plasma wakefield accelerators and free-electron laser linacs continue the drive to ever-shorter bunch durations. In low-charge operation (∼20  pC), bunches shorter than 10 fs are reported at the Linac Coherent Light Source (LCLS). Though suffering from a loss of phase information, spectral diagnostics remain appealing as compact, low-cost bunch duration monitors suitable for deployment in beam dynamics studies and operations instrumentation. Progress in middle-infrared (MIR) imaging has led to the development of a single-shot, MIR prism spectrometer to characterize the corresponding LCLS coherent beam radiation power spectrum for few-femtosecond scale bunch length monitoring. In this Letter, we report on the spectrometer installation as well as the temporal reconstruction of 3 to 60 fs-long LCLS electron bunch profiles using single-shot coherent transition radiation spectra
First documented deep submarine explosive eruptions at the Marsili Seamount (Tyrrhenian Sea, Italy): A case of historical volcanism in the Mediterranean Sea
The Marsili Seamount (MS) is an about 3200 m high volcanic complex measuring 70 × 30 km with the top at
~500 m b.s.l. MS is interpreted as the ridge of the 2 Ma old Marsili back-arc basin belonging to the Calabrian
Arc–Ionian Sea subduction system(Southern Tyrrhenian Sea, Italy). Previous studies indicate that theMS activity
developed between 1 and 0.1 Ma through effusions of lava flows. Here, new stratigraphic, textural, geochemical,
and 14C geochronological data from a 95 cm long gravity core (COR02) recovered at 839 m bsl in theMS central
sector are presented. COR02 contains mud and two tephras consisting of 98 to 100 area% of volcanic ash. The
thickness of the upper tephra (TEPH01) is 15 cm, and that of the lower tephra (TEPH02) is 60 cm. The tephras
have poor to moderate sorting, loose to partly welded levels, and erosive contacts, which imply a short distance
source of the pyroclastics. 14C dating on fossils above and below TEPH01 gives an age of 3 ka BP. Calculations of
the sedimentation rates from the mud sediments above and between the tephras suggest that a formation of
TEPH02 at 5 ka BP MS ashes has a high-K calcalkaline affinity with 53 wt.% b SiO2 b 68 wt.%, and their composition
overlaps that of the MS lava flows. The trace element pattern is consistent with fractional crystallization
from a common, OIB-like basalt. The source area of ashes is the central sector of MS and not a subaerial volcano
of the Campanian and/or Aeolian Quaternary volcanic districts. Submarine, explosive eruptions occurred atMS in
historical times: this is the first evidence of explosive volcanic activity at a significant (500–800 m bsl) water
depth in the Mediterranean Sea.MS is still active, the monitoring and an evaluation of the different types of hazards
are highly recommended.Published764-7742IT. Laboratori sperimentali e analiticiJCR Journalrestricte
First documented deep submarine explosive eruptions at the Marsili Seamount (Tyrrhenian Sea, Italy): A case of historical volcanism in the Mediterranean Sea
The Marsili Seamount (MS) is an about 3200 m high volcanic complex measuring 70 × 30 km with the top at
~500 m b.s.l. MS is interpreted as the ridge of the 2 Ma old Marsili back-arc basin belonging to the Calabrian
Arc–Ionian Sea subduction system(Southern Tyrrhenian Sea, Italy). Previous studies indicate that theMS activity
developed between 1 and 0.1 Ma through effusions of lava flows. Here, new stratigraphic, textural, geochemical,
and 14C geochronological data from a 95 cm long gravity core (COR02) recovered at 839 m bsl in theMS central
sector are presented. COR02 contains mud and two tephras consisting of 98 to 100 area% of volcanic ash. The
thickness of the upper tephra (TEPH01) is 15 cm, and that of the lower tephra (TEPH02) is 60 cm. The tephras
have poor to moderate sorting, loose to partly welded levels, and erosive contacts, which imply a short distance
source of the pyroclastics. 14C dating on fossils above and below TEPH01 gives an age of 3 ka BP. Calculations of
the sedimentation rates from the mud sediments above and between the tephras suggest that a formation of
TEPH02 at 5 ka BP MS ashes has a high-K calcalkaline affinity with 53 wt.% b SiO2 b 68 wt.%, and their composition
overlaps that of the MS lava flows. The trace element pattern is consistent with fractional crystallization
from a common, OIB-like basalt. The source area of ashes is the central sector of MS and not a subaerial volcano
of the Campanian and/or Aeolian Quaternary volcanic districts. Submarine, explosive eruptions occurred atMS in
historical times: this is the first evidence of explosive volcanic activity at a significant (500–800 m bsl) water
depth in the Mediterranean Sea.MS is still active, the monitoring and an evaluation of the different types of hazards
are highly recommended