Developing the LDMX Detector
Nothing is quite as wonderful as the honeymoon period of developing a new experiment. You don't have to think about how things will work exactly, of how annoying it will be to overcome the most difficult hurdles: anything is possible!
First comes the physics, the idea that you would like to explore, then you begin to think about what it would take to make it happen. More often than not, you find that some major leaps would be required to realize your idea, so you set it on the back burner until a light goes on about how to make such a big leap. However, occasionally you find that most, perhaps even all, of the elements you need exist somewhere in some form and all you need to do is figure out how to get them all together. That was pretty much the case for the Heavy Photon Search (HPS) detector, and so it is for the Light Dark Matter Experiment (LDMX). LDMX is a close cousin to HPS, but instead of looking for a dark photon, LDMX looks for light dark matter which needs something like a dark photon to exist in order to interact with normal matter. One of the puzzle pieces we need is a big dipole magnet, like the one I'm sitting on in this picture which has been sitting in End Station A at SLAC for decades just waiting for someone to call it's number.
Of course, even if the basic technology exists for your experiment, it's never easy. If it were easy, someone would have done it before. However, starting from scratch comes with complete freedom: nothing is set in stone and anything is possible. It's a puzzle with only one rule: doing the physics as well and as simply as possible.
Then, over time, you have to figure out how to make all your pretty ideas real. The beautiful detectors grow cables, connectors, supports and all kinds of ugly little bits that are simply no fun to deal with. All those parts are critical, though, and once the honeymoon is over and you are in the real work of making the experiment work, you're finally where you worked so hard to get: close to answering the question that started the romance in the first place.