SL75/20 dual energy linear accelerator introduces new technology in the NKI

SL7520 install kl.jpg 

1973. During the installation of the SL75/20 linear accelerator in the NKI. From left to right: Rein Helmink (engineer NKI); Stan Taylor (Philips-MEL), Charles Ashman (project leader Philips-MEL), Henk van der Gugten (engineer NKI).

The Netherlands Cancer Institute (NKI) orders Philips' new model of linear electron accelerator (linac) of the type SL75/20, which is still under development. This will be the first linac having a choice between two powerful photon energies of 8 and 16 MV (megavolt), in addition to eight electron beams with energies of 4, 6, 8, 10, 12, 14, 17 and 20 MeV (mega-electron-volt).

The Philips-MEL division (from Crawley, Great Britain) installs  one of the two prototypes of the SL75/20 in the NKI. The head of the development group of Philips-MEL, Charles Ashman, supervises the installation in Amsterdam.

On completion of the SL75/20 accelerator, Philips is permitted to make a film commercial in the treatment room of the NKI-AVL. In order to create an authentic atmosphere the cast consists of co-workers of the hospital. A summary of this film can be seen in another item on the timeline, in 1975:  Summary of the film commercial of Philips about the SL75/20. 

The cooperation between Charles Ashman and the physics-technical group of the NKI results in a long lasting working relationship. Philips-MEL provides knowledge and parts that allow the NKI to perform fundamental adaptations and revisions of Philips accelerators.

1976 SL75_10 modulator upgrade web.jpg

Modulator and control cabinet of the SL75/super accelerator after the modernization.

In 1976, the SL75/super accelerator is modernised by the NKI group. The stability and the reliability of the radiation beams and the dose measuring system are improved. In addition to the 8 MV photon beam, electron beams of 6, 8, 10, and 12 MeV become available.




Technical details:

  • The  high voltage pulse modulator is fitted with power stabilization by means of de-queuing. In this way the accelerator is functioning more stable.
  • The glow current regulation of the electron gun is upgraded with modern electronics and feedback of the dose signal. In this way the photon energy is stabilized.
  • Fitting of a multi-segment ionisation chamber in the treatment head of the accelerator and new dosimeter circuits allowing dual channel  independent dose measurement.
  •  Electronic stabilization of the beam symmetry and energy.
  • A new control panel for the radiation therapist providing the extra space for the new electronics.  
1973 bediening SL75super oud.jpg
1975 ca SL75_10 AVLmod.jpg

Left: the original control panel of the SL75/super. Right: the control panel as modernized by the NKI group. The construction, the functionality and the controls have been made identical to the newly installed SL75/20 accelerator.