Design Overview


AESOP-Lite on lab stand


SolidWorks schematic of the instrument


The AESOP-Lite instrument is a simple magnet spectrometer which inherits some of its components from the LEE telescope:

  • 3 scintillators (T1, T3, and T4) are used as the online trigger signal
  • 1 scintillator (guard) used offline as a anticoincidence signal
  • Cherenkhov threshold detector (T2) filled with C3F8 gas for hadron and backward particles identification
  • Magnet spectrometer, using a 0.3 T dual ring dipole magnet and seven planes of silicon strip detector trackers, 4 in the bending plane, 3 in the non-bending plane for a full 3D view of the particle trajectory

Tracking System


One of the seven tracker boards: each one is made up of 4 SSDs wire-bonded together vertically

The tracking system, developed at UCSC, was especially designed for the Fermi/LAT satellite instrument. It has been reused for multiple experiment such as the Proton Computer Tomography scanner (pCT), and now AESOP-Lite.

Each strip is connected to 12 front-end chips, with 64 channels each, adding up to 768 channels per board. With a strip pitch of 228 μm, the detector yields a spatial resolution σ = 66 μm





Tracker boards being tested at U


Example of a reconstructed straight cosmic ray track

Calibration ground runs have shown the tracker reaching an excellent efficiency of about 97% per layer.


The magnet spectrometer will use dual “ring dipole” permanent magnets using the Halbach design. The dual magnet design allows placement of a tracker plane at the  center of the magnetic field to optimize resolution without requiring complex wiring to the detector. The 0.3 T field is largely non-uniform, a complication that is accounted for in the particle reconstruction analysis.


AESOP-Lite magnetic field lines


AESOP-Lite magnet


%d bloggers like this: