(Stockholm Skolors Kosmiska Nätverk)


VH logo





[Subatomic Rain]  [SEASA]  [Documents] [For students] [Contact]  [Related]



I n t r o d u c t i o n

The Stockholm Educational Air Shower Array (SEASA) project was founded in 2002 by the KTH Particle and Astroparticle Physics group with the goal of bringing the intellectual and technical challenge of scientific research to high-school (gymnasier) students. The project illustrates how research is conducted today and offers a modern and concrete focus for student project work in the final year of high-school studies. Students gain experience working with advanced instrumentation to produce data that is relevant to cutting-edge research while the project itself is dimensioned so that students are able to make significant contributions. Students also discover that the desired scientific results can only be achieved through collaboration between the participating schools.

The focus of the project is the study of high energy cosmic ray showers using a network of GPS time-synchronised cosmic ray detector stations established during 2005 at participating schools in the Stockholm region.

The following schools participate:

As from September 2007,  SEASA is run in collaboration with  'Vetenskapens Hus'  (The House of Science)  which is co-located at AlbaNova  University Centre along with the KTH Physics Department.

SEASA is a member of the Eurocosmics initiative which aims to co-ordinate similar projects across Europe.

T h e  S u b a t o m i c  R a i n

Subatomic particles from space constantly rain down on the earth's atmosphere. Most of these particles are protons accelerated to huge energies by shock waves produced in supernovae explosions. The protons interact with gas molecules at the top of the atmosphere producing further subatomic particles which can also interact with the atmosphere or decay. The net result is a shower of particles which move towards the earth's surface.

An artist's impression of the shower of subatomic particles produced when a cosmic ray proton collides with the top of the earth's atmosphere.

For the highest energy protons, these showers contain billions of particles and cover an area of many tens of square kilometres. By intercepting the particles as they hit the ground the properties of the original cosmic ray proton hitting the top of the atmosphere can be determined. The energy of the proton and its arrival direction are of particular interest as the nature and location of acceleration sites can be probed. 

Supernovae shock waves are thought to be the acceleration sites for cosmic rays. In this picture, the hot remnants from a supernova explosion have been imaged with the X-ray photons they emit.

The energy spectrum of cosmic rays at the top of the earth's atmosphere. The energy scale (in units of electron-volts) spans more than 10 orders of magnitude!


The aim of SEASA is to contribute to the knowledge of cosmic ray air showers but with a particular emphasis on education. Low cost particle detector stations have been developed and have been installed at schools in the Stockholm area. The schools form a distributed detector array which will intercept the shower of particles as they reach the ground. Air showers can be identified by checking the arrival times of particles at different detector stations. Since the detector stations could be separated by several kilometres, signals from GPS satellites are used to establish a common timing reference. As more and more schools join this effort, higher and higher energy cosmic ray showers will be able to be detected. The study of so-called Ultra High Energy Cosmic Ray (UHECR) showers is a hot topic in contemporary particle astrophysics.

An array of detectors laid out on the ground intercepts the shower of particles produced when a high energy cosmic ray proton strikes the top of the atmosphere. The size of the air shower footprint on the ground is related to the energy of the initial proton. The direction of the initial proton can be estimated by considering the time differences between the shower front hitting adjacent detectors.

A view of one of the detector stations located atop AlbaNova University Centre in Stockholm. The three scintillator detectors and GPS antenna (while dot to left of image) can be seen. The Brunnsviken lake is visible in the background.

D o c u m e n t s

Original design document


Selected publications and talks

F o r  S t u d e n t s

C o n t a c t 

KTH: Mark Pearce / pearce .at. (replace '.at.' with '@') / 08 -55378183.

Vetenskapens Hus: Cecilia Kozma /  cecilia.kozma .at. replace '.at.' with '@') / 08 -55378781

R e l a t e d  p r o j e c t s

There are similar projects to SEASA around the world. In Europe, most of the projects participate in the Eurocosmics intitiative. There are also activities in North America.

You may also be interested in two related projects at KTH dealing with the cosmic radiation: