Experiences in the superconducting quadrupole prototype magnet development for SuperKEKB

The beam final focus superconducting magnet system for SuperKEKB consists of 55 superconducting magnets, and it is a key system for increasing the electron and positron beam collision frequency. In particular, high quality of the superconducting quadrupole magnet close to the interaction point for each beam was requested in the excitation and magnetic field performance. KEK developed the prototype quadrupole magnets in house. This paper reports on the many conditions experienced during development of the prototype magnets. (author)