Activity Report(Vol.10:17/5/2013)

We held the ScienceCafe@Fukuoka Vol.10 at Kyushu in Japan!

Japanese Page

Poster Vol.10

 This time's subject was "Capturing Elementary Particles"!
 Through previous events, we had learned about "theories" of physics and approached the ILC(International Linear Collider). But we didn't have taken up any topics about "experiment". Finally, our wish came true this time! we learned about experimental equipments called "Detector".

 I was glad to meet you, everyone!

First Session

 First of all, we had a brief lecture about the history and principle of detectors!
 Today's lecturer were Dr.Yoshioka(Kyushu Univ.) and a master's student Koura.
 Koura is also the author of recent activity reports. I'm now reporting about me by myself.

Lecturers:It's me!(left) and Dr.Yoshioka(right)

 We put on white coats because it looks very very very cool!!Actually, researchers of experimental elementary particle physics don't wear white coats.

 Let's review the lecture!

What does it really mean about looking at an apple?

 Before we learn how to look elementary particles, let us think about how the "looking" is executed. For instance, assume that there is an apple in front of you.

 Of course, you look it with your eyes and think "There is an apple with red color". We can look something only with eyes?The answer is NO. There should be one more important thing. That's the "light".

 We can look an apple by capturing the light reflected on the surface of it with eyes. "Looking" intrinsically means "capturing the light reflected by something with eyes". And then, let us consider "looking elementary particles" by replacing an apple with elementary particles.

 Surprisingly, elementary particles are so small that the light can't hit them. If the light could hit them, they were flicked off by its impact. We can't look elementary particles directly by using the light because of its phenomenal smallness!

Looking Particles Indirectly by Using Their Characteristics!

 Should we give up to look elementary particles? No, there is other way. Elementary particles(radiations) have some unique properties.

  • Ionization
     Elementary particles remove electorons from atom which they hit!(ionization)
  • Scintillation
     Specific materials can emit the light when elementary particles pass through them!
  • Photographic effect
     Photographic plate get blackened by elementary particles!

 These properties make elemetary particles visible indirectly!Then, physicists create experimental equipments called "Detector" which make use of them.


 There are so many kind of detectors. Here, I explain two different types of them, "Cloud chamber" and "Scintillation counter".

  • Cloud chamber
     Clooud chamber is probably a first practical detector. It was developed in 1897 and had used in particle physics study until 1950s. It makes use of ionization property of elementary particles and make their tracks visible as cloud.

  • Scintillation counter
     The materials that emit the slight light when elementary particles pass through them are called scintillators. Photomultiplier tube(PMT) is the device that coverts the slight light to the electric signal. The combination of scintillator and PMT is scintillation counter.

 There are many other detectors. But almost all of them also use same principle refered above fundamentally.

The Detector of ILC

 At last, we approached the detector of ILC
 There will be two kind of detectors at ILC. First, the SiD(Silicon Detector) which is developping in America mainly. Second, the ILD(International Large Detector) which is developping in Japnan and Europe mainly. Both are larege and complex detectors consist of several different detectors. Their structures are unbelievably complicated but the principle of each devices are same notions mentioned above.

Let's Experiment!

 We observed electric signal generated by cosmic ray which is elemaentary particle coming from space with scintillation counter!And then, we observed α-ray with cloud chamber!It was so exciting experience!

Second Session

 Next session is talking-time with all participants.
 Everyone asked many good questions!I had a very good time!

Next Event

 Next ScienceCafe@Fkuoka will hold on 21 June(Fri)!
 The subject is "Let's Go to the Space!".
 Dr.Hirayama(Kyushu Univ.) will invite everyone to the vast space.