Microscopes status Andrey Alexandrov

Microscopes’ Status Napoli LNGS NSSna1 (aka mic6) – used for measurements for plasmon analysis LC recalibrated for use with the blue light NSSna2 (aka mic4) – ready for measurements for ML color analysis Requires implementation of the offline cluster reconstruction for color images LNGS NSSgs1 – used for emulsion quality check Requires an intervention to correct the anisotropy in the ellipticity distribution and enable the shape analysis NSSna1 and NSSgs1 were actively used in last months and no serious update was possible

Recalibration of the LC @ NSSna1 The LC is designed to operate in the violet light ( = 405 nm) During the optimization campaign the violet LED was replaced with the blue one ( = 460 nm) The actual polarization angles do not correspond to those expected: 28.7 Extra image with pol = 0 The actual range is [0 – 128.8] instead of [0 – 157.5] Recalibration of the LC is required

Recalibration of the LC @ NSSna1 Use the “rotating cluster shadows” to monitor the actual polarization angle Adjust the voltage mapping in LASSO ~2.5 Extra image with pol = 0 The actual range becomes [0 – 155] instead of [0 – 157.5] The LC voltage range is not sufficient

Low-energy C-ions detection problem Andrey Alexandrov

“State of the Art” Spatial accuracy = 5 nm Spatial accuracy for X and Y “State of the Art” Spatial accuracy = 5 nm Length measurement accuracy = sqrt(2)*5 = 7 nm Detection threshold = 3*7 = 21 nm

Detection threshold definition problem Expected mainly single grain tracks for 10 keV C ions Expected that almost all events are rejected for 10 keV sample The definition of the threshold is not compatible?

Threshold definition through the barshift CDF Require that 95% of events are rejected for the 10 keV sample Detection threshold = 44 nm Detection efficiency for 30 keV C-ion = 13.8%

30 keV C-ions An evident peak below the threshold BS > 44 nm

10 keV C-ions BS > 44 nm BS < 44 nm Also for the 10 keV vertical sample the same peaks are visible Tiny vibrations (~1-2 nm)? Spatial accuracies are different for X and Y axes (5 nm vs 4.7 nm) Stronger vibrations along X axis?

Correction of vibrations with frame alignment Select 8 images with different polarizations and the same Z Match clusters and calculate offsets w.r.t the first image (pol=0) Apply same offsets to all clusters in the same image For a successful alignment at least 40 matched clusters are required X corrections ~3 nm Y corrections ~1.5 nm

Spatial accuracy and detection threshold for aligned samples 10 keV C-ions Spatial accuracy ~4.9 nm for both X and Y Detection threshold (@95%) = 42 nm Barshift length CDF

10 keV C-ions dataset after alignment BS > 44 nm BS < 44 nm BS > 42 nm BS < 42 nm BS > 42 nm BS < 42 nm More flat angular distribution below the threshold (but not perfect) More flat above the threshold (too low statistics) Efficiency = 5%

30 keV C-ions dataset after alignment BS > 44 nm BS < 44 nm BS > 42 nm BS < 42 nm BS > 42 nm BS < 42 nm Flat angular distribution below the threshold Peak above the threshold (efficiency = 12.4%) Peak width (0.45) is close to that of 60 and 100 keV C-ions (0.41 and 0.42)

Conclusion Seems that tiny vibrations still exist and hinder measurements at low energies The new threshold definition with using 95% of the barshift CDF is good for aligned datasets Problem: we cannot use alignment for real measurements Need to confirm that the peak for of the aligned 30 keV C-ion sample is due to the ion tracks => rotate the sample and rescan => in progress Need to develop a routine to “subtract” vibrations => Scan twice (with sample’s rotation of 0 and 90) and process the combined dataset? => in progress Will require double time for scanning! The ultimate solution is to construct the microscope not sensitive to vibrations