Categories of exhibits
MALDI laser beam attenuator
Exhibit no. 944
UV lasers are frequently used in MALDI mass spectrometry. An appropriate laser power (energy delivered per unit area sampled) must be used for the ionization. Increasing the laser power beyond the threshold can increase the analyte signal intensity, but too high power can cause the signal to become saturated, leading to incorrect peak shape. The power of a laser beam can be modified with optical attenuators. In circular reflective neutral density filters, the degree of attenuation continuously varies along a circle around the axis of rotation. The filters are made of a UV fused silica glass substrate with a metallic coating.
The exhibit is an optical bench with a laser attenuator, which was located in a laser housing of a MALDI-TOF mass spectrometer Reflex IV. The instrument was manufactured by Bruker Daltonics in the 2000s. The instrument used a nanosecond pulsed nitrogen laser at 337 nm. After deflecting a small percentage of the laser beam onto a trigger diode, its main part continued straight through the attenuator wheel. Two lenses on the optical bench and a mirror served to focus the beam and reflect it through a quartz vacuum window onto the target plate. Rotation of the laser attenuator wheel was controlled from the instrument software.
