Vacuum pump play in piston

Does anyone know if there is supposed to be this kind of play in the piston of a vacuum pump for a 300tdi.
Measurement are taken at the end of the stroke and up to the point where the piston meets the spring tension. This allows for 3 mm of freeplay, im not sure if there is such play when it is installed.
I have a ticking noise, i believe it might be the pump, the surface also looks to be a bit hammered.

Mine has the same kind of play as well . Was like that from new.
As for the ticking not sure but you should be able to get a good look at the lobe/lobe's on the camshaft too see how that looks as there is plenty space.

I’ve just changed mine on my 300tdi. I had a hard brake pedal and braking was a bit dubious. No play on the old pump or new one and braking back to ‘normal’! Was your braking being affected.
I got a new one from Turner’s.

Braking seems to be normal and there has not been any problems there, only symptoms has been a progressively louder ticking, on a warm engine the ticking is louder than the engine especially on higher rpm.

But is it correct to assume that there shouldnt be this kind of ''play'' on the piston

Went back and looked at my old pump. the piston has about 3mm of play back and forward in it. Hate to say it but that loud ticking could be a head gasket. Your describing the same sound I had and the head gasket was blown at the back of number 4 cylinder. I put my hand round the head and could feel the air getting out. It started as a ticking noise just like you described. I changed the pump when I had the engine stripped down to do the head as the access was easier and knew I had an issue with the assistance to the brakes. Check yours out and how it looks.