ERDA-ToF beamline image

View of the ERDA-TOF beamline

inside of ERDA-TOF beamline image

Inside of the ERDA-ToF analysis chamber showing the rotatable sample holder

Responsible scientist: Andrés Redondo Cubero

The Time-of-Flight (ToF) beamline at CMAM was designed to perform Elastic Recoil Detection Analysis (ERDA) experiments with simultaneous detection of the particle’s energy and time of flight. The ERDA-TOF method is of particular interest in determining the depth profile of light elements from the surface region to depths of up to several micrometers.

By the end of 2009, the Time of Flight (ToF) beamline at CMAM was completely assembled and the first tests were performed in 2010.

ToF beamline is located at the 10º port of the first switching magnet at the exit of the accelerator, allowing for work with high mass and low charge state ions. In the beam line, two sets of four independent slits are located in order to define the beam spot on the sample, which is positioned by means of a 3-axis  goniometer inside the scattering chamber. The incident beam current can be measured continuously during the experiment by means of a Transmission Faraday Cup situated at the entrance of the chamber. A Time of Flight telescope, placed at 40º from the beam, collects the particles, measuring both energy and time of flight for each particle.

To measure the time of flight, two time stations are placed inside the telescope. The length of flight between them can be adjusted, being 42 cm the nominal value. When a particle crosses a time station, a fast signal is generated. This signal is used to feed Fast Preamplifiers and Constant Fraction Discriminators. A time-to-amplitude converter is used to obtain a pulse with a height proportional to the time of flight between the two detectors. At the end of the telescope, a solid state detector measures the particle energy. Both time and energy signals are recorded in list mode, the amplitude and the time of every event is recorded.

Real time or further software treatment allows determining which events occurred in coincidence, making possible mass determination for each detected particle. For heavy particles, energy spectra obtained form time spectra have a much higher resolution than the ones obtained directly from energy detector.

ERDA-TOF spectra

In addition to the ToF detection telescope, an extension in the direction of forward scattering has been added, which has been used for several experiments which do not require the ToF  detector. A silicon drift X-ray detector (KETEK AXASA) has also been installed and used in several experiments.