The blocks immediately around Tsukuba Station have a handful of ramen shops serving the local workforce and the steady stream of day-trippers from Tokyo. Tsukuba leans toward rich tonkotsu and miso-based broths, suited to the cold winters on the Kanto Plain. Lunchtime is the prime window — many shops open around 11am and close once the day's broth is gone, often by mid-afternoon.
The area around the Tsukuba Center bus terminal is the densest concentration. Look for the handwritten menus in the windows and the short queues at lunchtime as a quality indicator — a ramen shop that locals queue for is reliable. Most do not take reservations, but turnover is quick. Prices are reasonable: a bowl with a side of rice or gyoza typically comes to around 1,000–1,200 yen.
For a town of its size, the competition between shops keeps quality up. If you are arriving on the Tsukuba Express after a morning at JAXA, a bowl near the station is a natural way to round off the visit before heading back to Tokyo.