Home page of Fred Hartjes

Contact Last update August 8, 2020



Assembling the Lepcol eight quad testbox, February 2019

My life as a retired person

At my formal farewell from Nikhef on January 27, 2011, the director Frank Linde referred to the diamond on the invitation card, suggesting that I should continue my presence at Nikhef until my diamond anniversary, i.e. September 2026. Although I am still active on Nikhef based projects for about 6 hours a day, I cannot guarantee that I will make this.

For the rest live is easy and enjoyable now as a retired person with good health, giving me peace for things like Anker stones and mending my garden at my holiday home in Koekange (Drenthe), altogether with my dear wife Josephine.

My activities

Developing a gas-filled pixel Time Projection Chamber at Nikhef

  • Using GridPix detection technology
    • GridPix: A thin grid is attached onto the pixel chip. By applying a negative potential to the grid the single is multiplied by a gas avalanche
  • The detector elements
    • Present Quad from four TimePix3 chips (more info)
      • 12 operational quads have been realized
    • Future Single from one TimePix4 chips
      • Project not yet started
  • Grouping the elements to form a larger detector system
  • Testing the detectors
    • UV laser beam
      • Thesis Univ. of Amsterdam, Nov. 6 1990 (43 Mb)
    • Testbeam
  • Ionic investigations
    • Positive ions that could spoil the drift field
      • Originating from direct ionization and avalanche leakage through the grid
    • Negative ions from electrons captured by electronegative gases
      • CS2 investigated

The investigations and developments are done in the framework of the ILC (International Linear Collider) initiative at Nikhef.

Spark chambers

To demonstrate cosmic rays spark chambers are available at Nikhef.

Anker stones