The Physics of Healing: Radiation Therapy

Few days are worse than a day when you hear the words, “I’m sorry, you have cancer.” Fear of the unknown, fear of pain, and fear of death all attend the moment when you learn the news, and nothing can prepare you for the shock of learning that your body has betrayed you. It can be difficult to know there’s something growing inside you that shouldn’t be there, and the urge to get it out can be overwhelming.

Sometimes there are surgical options, other times not. But eradicating the tumor is not always the job of a surgeon. Up to 60% of cancer patients will be candidates for some sort of radiation therapy, often in concert with surgery and chemotherapy. Radiation therapy can be confusing to some people — after all, doesn’t radiation cause cancer? But modern radiation therapy is a remarkably precise process that can selectively kill tumor cells while leaving normal tissue unharmed, and the machines we’ve built to accomplish the job are fascinating tools that combine biology and engineering to help people deal with a dreaded diagnosis.

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Open Source Cloud Chamber

If you are a certain age, there were certain science toys you either had, or more likely wanted. A chemistry set, a microscope, a transparent human body, and (one of several nuclear toys) a cloud chamber. Technically, a Wilson cloud chamber (named after inventor Charles Wilson) isn’t a toy. For decades it was a serious scientific tool responsible for the discovery of the positron and the muon.

The principle is simple. You fill a sealed chamber with a supersaturated water or alcohol vapor. Ionizing radiation will cause trails in the vapor. With a magnetic field, the trails will curve depending on their charge.

If you didn’t have a cloud chamber, you can build your own thanks to the open source plans from [M. Bindhammer]. The chamber uses alcohol, a high voltage supply, and a line laser. It isn’t quite the dry ice chamber you might have seen in the Sears Christmas catalog. A petri dish provides a clear observation port.

We’ve covered cloud chamber builds before, ranging from the simple to ones that use thermoelectric coolers.