4 minute read
Hi, I’m Sam Flynn from the Radiotherapy and Radiation Dosimetry (RadDos) group at NPL. I’m currently on secondment to our international counterparts – the Metrology Research Centre at the National Research Council of Canada (NRC) in Ottawa, Canada. This blog is part of the Kamal Hossain International Secondment Scheme. If you missed the first blog post, you can catch up here.
April here in Ottawa has been a very weird month for weather, I think I’ve gone through a year’s worth of seasons. It’s become very clear that I’ve not packed enough winter or summer clothes!
A big aim from this secondment is to immerse myself in how NRC metrology operates and identify things that they do differently to NPL and understand why they’ve done this and what impact it has. Some differences are small, but interesting. The NRC defines reference conditions at 22°C, while in the UK and Europe it’s generally 20°C. Similarly, we position the chambers between 5-7 cm deep in water (energy depending); the NRC uses a static 10 cm.
Neither approach is inherently better: as long as these conditions are agreed and understood between the national metrology institute and the end user, the calibration chain remains robust. It’s definitely something to be aware of when conducting international comparisons however!
The biggest difference lies in our primary standards for absorbed dose. I mentioned in my last blog that the NRC uses water calorimetry, while NPL uses graphite. The theory is one thing but putting it into practice is another. The water needs to be periodically stirred, cooled, and heated to maintain a specific temperature (4 °C), and the measurements are slow, methodical, and precise. I’ve been getting as stuck in as possible trying to absorb as much knowledge as I can, expect most blogs to mention calorimetry in one way or another! Realising absorbed dose, both here and at NPL, takes weeks to complete.
No trip to Canada is complete without catching an ice hockey game! I was able to watch the Ottawa Senators beat the Philadelphia Flyers with a dramatic overtime goal – thank you to my NRC hosts for setting this up and accompanying me on a lovely day out. Sadly, the Senators didn’t make it far in the Stanley Cup playoffs, losing the “Battle for Ontario” against the Toronto Maple Leafs. Still, it was fun while it lasted…!
I’ve also had the opportunity to give a seminar at the Ottawa Medical Physics Institute (OMPI), held at Carleton University. This is a multi-institute medical physics network led by Malcolm McEwen (NRC) to support a broad range of research activities across radiotherapy, medical imaging, and more. It was an excellent opportunity to share some of the work I’d been doing at NPL before this secondment and to hear about the other activities going on in Ottawa. There’s definitely scope for future collaboration!
19 May 2025