How to calculate the momentum of an electron ? Measuring the radius of curvature in a magnetic field … 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

They go on spirals if they are also loosing energy If electrons are entering a magnetic field, they are forced to go on a circle. They go on spirals if they are also loosing energy 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

The Lorentz-law helps to describe this behaviour : 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

Dora Wagner & Miguel Vieira HST 2001 goes into the page ! 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

Dora Wagner & Miguel Vieira HST 2001 The Lorentz-force is the centripetal force, which pulls the electrons to the centre : 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

Look at this sketch… …click it ! 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

Dora Wagner & Miguel Vieira HST 2001 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

How to measure the radius ? 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

Dora Wagner & Miguel Vieira HST 2001 If we know the radius r … 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

… and if we know the strength of the magnetic field B… 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

… we are able to calculate the momentum : 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

Dora Wagner & Miguel Vieira HST 2001 Try it ! What to measure, what to know Scale 1 : 6.4 For more information click here 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

Dora Wagner & Miguel Vieira HST 2001 In the Fermilab where this picture was taken, the magnetic field was : B = 3 Tesla The charge of the observed electron is : e = 1.6x10-19 Coulomb 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

Dora Wagner & Miguel Vieira HST 2001 Are you able to use the Pythagoras theorem to calculate the radius r from L and D ? BACK 07/17/2001 Dora Wagner & Miguel Vieira HST 2001

A photon traveled between the two marked points A photon traveled between the two marked points. The traveled distance was, in the real experiment, 11.5 cm! If you want to know more,click-me 07/17/2001 Dora Wagner & Miguel Vieira HST 2001