Kategorie: Articles

Superconductivity

There are materials that have zero electrical resistance if the temperature is sufficiently low. Also the current density and the magnetic field should not be too high. In 1908 Heike Kamerlingh-Onnes and his laboratory accomplished to liquify helium whose boiling temperature is about 4.2 K under atmospheric pressure. Thus he could discover the superconductivity of mercury in 1911.

In the following years many other superconductors have been discovered, even high temperature superconductors (HTS). HTS has the advantage that liquid nitrogen (77 K) is sufficient.

Superconducting magnets often consist of niobium titanium (NbTi) that has a critical temperature of approximately 10 K.

The colder part of current leads is frequently built with HTS for very large currents.

 

Heavy Ions

The title refers to the double meaning of heavy. It is employed in physics as well as in music, only think of heavy metal. Thus a piece of tonal physics was created and performed at the barbecue of the Jazz & Pop School in 2018. When you listen to the recording, I recommend to close your eyes. Imagine you are chasing through the vacuum of the beam pipe with so many other ions of your bunch almost at the speed of light. Again and again you are accelerated by high frequency cavities, being kept on track by superconducting magnets.  🙂

The lead sheets:

Schwere_Ionen_C   Schwere_Ionen_Bb   Schwere_Ionen_Eb

 

Wavy Falling Films

As an example from the broad field of wavy falling films we take a simulation created with OpenFOAM. The picture displays a water falling film of a Reynolds number of 60 being harmonically excited with a frequency of 13 Hz. Gravitation points from the left to the right. The control volume is 600 units long (in the direction of the stream). One unit is the thickness of the corresponding smooth film. The height (perpendicular to the stream) is equal to 4 units being magnified by a factor of 50.

The red colour marks the water, the blue the air. Downstream a certain pattern can be recognized: A large solitary wave and in front of it small capillary waves.

Easier Than Easy

First I composed a bossa with a lot of typical offbeat which I called Easy Bossa. It was never performed, since it seemed too difficult. Therefore only a Band in a Box version exists:

I simplified the Easy Bossa now calling it Easier Bossa. Still it is not easy, but easier.

In the Orangerie Garden Darmstadt the Jürgen Wuchner Workshop Band performed it in the summer of 2015. I especially like the relaxed atmosphere of the recording.

The lead sheets can be found here:

EasierBossa_C   EasierBossa_Bb   EasierBossa_Eb

 

Jets in QCD

What are jets? What does QCD mean?

The intuitive picture of a jet is a collimated spray of particles which is created by the collision of two particles in a high energy physics experiment. (There can be more than one jet.) Quantum chromodynamics (QCD) is the physical theory behind them. It states that a certain class of particles, hadrons, are built of quarks and gluons. If a quark or gluon is scattered, a jet is created. A quark or gluon has never been observed as a free elementary particle and QCD states that this is not possible. Instead after a scattering new particles are created very rapidly that can be observed. Regarded as a jet they have the momentum of the scattered quark or gluon. The exact definition of a jet is not trivial and there are sophisticated algorithms to find them.

Why are jets interesting to physicists?

With their aid conclusions can be made on the fundamental process without having to measure a free quark or gluon.

Falling Films

In process engineering a falling film is a thin liquid film which flows down an inclined plate by the action of gravity. Falling films are employed in various fields, like the food industry, the pharmaceutical industry or in power plants. They have the advantage of a good heat transfer and a small hold up. Furthermore, they have a large surface for the exchange between gas and liquid (like in gas scrubbing).

A falling film flowing down a vertical wall is always hydrodynamically unstable. However, if the Reynolds number is very small, the waves may not be seen.

In the EU project EasyMED I simulated evaporating seawater falling films. Turbulence wires were employed to improve the heat transfer.

Tritone Blues

This is a blues which sounds a bit off-key, but where I stay within the harmonies. It has been performed for several times. Here you can listen to a recording I made at home with a guitarist and a bass trombone player. I played the soprano saxophone. Bass and drums came from Band in a Box, i.e. from the computer.

Where does the name come from? The tritone is a dissonant interval consisting of three whole steps. For improvisation you should play the third and the seventh. However, between the major third and the minor seventh, there is the tritone. Take, as an example, the chord C7. The third is E and the seventh Bb. There are mainly dominant seventh chords in the blues. Thus I could compose a blues with many tritones.

You can find the lead sheets here:

TritoneBlues_C   TritoneBlues_Bb   TritoneBlues_Eb

 

The Plug Calorimeter

I am going to summarise my diploma thesis in plain words. It was a simulation of the ZEUS detector. ZEUS was the name of a collaboration which ran an experiment at the storage ring HERA in Hamburg, Germany. There, electrons and protons of high energy were brought to collision. Around the interaction point was the ZEUS detector covering almost the whole solid angle with the exception of the openings for the beam pipes. The idea for the plug calorimeter was to make the opening in the proton direction smaller. Thus the acceptance of the detector was enlarged. A calorimeter is an energy measuring device. The additional calorimeter was kind of a plug.

My first step was to implement several versions into the ZEUS detector simulation program MOZART. Then I simulated a test beam, i.e. I used a beam of particles of a single type with uniform energy. Finally, I tested with two kinds of electron proton scattering events. It could be demonstrated that these two types of scattering events can be much more easily separated in an analysis with the aid of a plug calorimeter.

A plug calorimeter was eventually built und installed. Finishing this article I want to mention a publication:

Bamberger et al., The ZEUS Forward Plug Calorimeter with Lead-Scintillator Plates and WLS Fiber Readout, Nucl. Instr. Meth. A450 (2000) 235-252 ( http://arxiv.org/abs/hep-ex/9912045 )

 

Japanese Bossa

This piece was performed during the Xmas Session 2015 at Jazz Institute Darmstadt by the Jürgen Wuchner Workshop Band.

You find the lead sheets here:

JapaneseBossa_C   JapaneseBossa_Bb   JapaneseBossa_Eb

I would like to add some remarks on the harmonic background. The melody consists of a Japanese pentatonic. This can be built by a major pentatonic where the major third is substituted by a minor third and the second note becomes the root. I give an example:

D major pentatonic: D E F# A B

Major third is substituted by minor third: D E F A B

Second note becomes root: E F A B D

When I harmonised the melody, I did not do the last step. To stay within the example, I kept D as the root.

 

Current Leads

Current leads are a cryo-electrical component of the circuit of a superconducting magnet, a pair for each electrical circuit. One end, the warm terminal, has ambient temperature, about 300 K (Kelvin). The other end, the cold terminal, has the temperature of liquid helium, approximately 4 K.

If the cross-section of the conductor is too large, a lot of heat comes from the warm to the cold terminal. On the other hand, if the cross-section is too small, the electrical current will cause a significant heating and the current leads may burn through. The designer has to find a compromise.

There are current leads which are only cooled at the cold terminal. This is the conduction cooled type. The vapour cooled current leads guide the helium vapour all along the whole length from the cold to the warm terminal. Sometimes the temperature is fixed in between with liquid nitrogen (77 K) by the employment of a thermal anchor.