microDiamond

Synthetic Diamond Detectors

OVERVIEW

  • Nearly water equivalent for all beam energies
  • Very small sensitive volume (0.004 mm³) - perfect choice for small field dosimetry
  • Suitable for all field sizes up to 40 cm x 40 cm
  • Precise, accurate measurements in photon, electron and proton fields
  • Excellent radiation hardness, minimal energy, temperature and directional dependence
  • No high voltage required. Suitable for all connecting systems
    (BNT, TNC, M)

microDiamond is the first commercially available single crystal diamond detector (SCDD) worldwide suitable for clinical dosimetry.
As a synthetic diamond detector, which is reproducibly manufactured in a new innovative production process, it combines the advantages of natural diamond detectors and silicon diode detectors almost perfectly. Due to its special design and material properties, microDiamond shows almost no deviations in absorbed dose to water even in the smallest field sizes, making it a perfect choice for accurate small field dosimetry.

The microDiamond detector was developed in cooperation with Marco Marinelli, Gianluca Verona-Rinati and their team at the Industrial Engineering Department of Rome Tor Vergata University, Italy.

How microDiamond works

Basic operating principle

A Schottky diode develops on the top contact. The incident radiation generates positive and negative charge carriers. These are separated by the field of the diode, thereby producing a signal current that can be measured with an electrometer. No external bias voltage is required; the microDiamond detector can (and should) be operated at 0 V.

microDiamond vs Silicon Diodes

As a synthetic diamond, the new microDiamond detector offers significant advantages over commonly used silicon diode detectors in terms of radiation hardness, temperature, energy and field size dependence.

Specifications

Type No. 60019
Design: waterproof, disk-shaped, sensitive volume perpendicular to detector axis
Measuring quantity: absorbed dose to water
Nominal sensitive volume: 0.004 mm³, radius 1.1 mm, thickness 1 µm
Reference point: on detector axis, 1 mm from detector tip, marked by ring
Nominal response: 1 nC/Gy
Detector bias: 0 V
Radiation quality: 100 keV ... 25 MV photons
(6 ... 25) MeV electrons
(70 ... 230) MeV protons
Field size: (1 x 1) cm² ... (40 x 40) cm²
Connectors: BNT, TNC or M

Minimal dose-rate and dose-per-pulse dependence

The dose rate can be varied by either changing the dose per pulse or pulse repetition frequency
of a linear accelerator. When measuring PDD and profiles, the dose per pulse changes.
Varying the dose rate of the LINAC changes only the pulse repetition frequency in most cases.
The microDiamond detector shows both a very small dose-per-pulse dependence (fig. top right)
and almost no dependence of the pulse repetition frequency (fig. top left) and continuous
dose rate (60Co, without fig.).

Minimum deviations in extremely small fields

Compared to other detectors used in small field dosimetry, microDiamond only shows a very
small deviation of absorbed dose to water even in the smallest field sizes starting from 0.5 cm x 0.5 cm
thanks to its special material and design properties.  

Detector comparison based on measurement results taken from P. Francescon et al.,
Med. Phys. 38 (2011), 6513, and W. Lechner et al., ESTRO Forum 2013

Excellent spatial resolution

With its excellent spatial resolution, microDiamond makes it possible to accurately measure profiles in very small fields as well as the penumbra region. As shown in the right figure, profiles measured with the high resolution PTW PinPoint ionization chamber 31014 (PP) and microDiamond (SCD) show an excellent agreement with each other across all field sizes in small field dosimetry.

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